I grabbed the link from an old blog post I made; I actually summarized the episodes too, which might help in looking for the ones you want. I think there's also a handful that post date that link, but you can still search for them by title at Wizards. I had very minor commentary on them, but you can mostly ignore that other than that I bolded the ones that I recall specifically address this issue either directly or indirectly.
-Surprise! Epic Goblins! — Go above and below the PCs level; not only to build verisimilitude and tension, but to also give the PCs challenges that they can't easily overcome, as well as opportunities to kick butt.
-Previously in Iomandra... — The quick summary the players need before each session starts; how to maximize.
-I Don't Know What It Means, But I Like It — use ideas as they come to you. They don't need to be fleshed out to introduce them. You don't have to know where they'll go. Throw them all out, see which ones the players latch on to, and go with it.
-My Campaign: The TV Series — how to adopt what makes good TV shows entertaining to your D&D campaign.
-Instant Monster — some specifically 4e related advice on how to reskin monster stats and make them up on the fly.
-Point of Origin — some great advice on how to make player characters immediately latch on to the world as part of chargen. Highly recommended.
-A Moment in the Sun — how to involve all of your players in the game, and give them all a chance to have the spotlight here and there.
-The Dastardly Duo — villain NPC advice.
-She Eats Babies! — more villain NPC advice
-Best Villain Ever — reader submitted villain NPCs
-Man Down! — when a player leaves the group (i.e. moving away out of state, in this case.)
-Big Map Attack — how to on making digital campaign maps
-Constellation of Madness — advice on being unpredictable as GM and giving challenges that challenge the players at least as much as the characters.
-Post Mortem — player character death and how to make the most of it
-Special Guest Star — a concept on having a guest player, and how to use them effectively to make the thing more fun for everyone.
-Popcorn — advice on using minions
-The Wyrmworn Experiment — working through an involving character arc (secret: it involves much less planning than you think, and no railroading...)
-Magnificent Minions — player submitted minions
-Joy and Sorrow — on the player contract, on mature players, and how to pull things off that challenge them without pissing them off.
-All Talk — on the combat-free session (and when to go ahead and indulge it anyway)
-It's About Time — using time travel to challenge your players (ed. no thanks)
-What's In a Name? — on names and NPCs and what kinds of development activities are actually useful to an under-preparing, wing-it style GM.
-Voice Talent — on modeling NPCs to make them memorable
-Intervention — the player who isn't on the same page as the rest of the group
-Maptism — site maps
-DM's Lib — don't over-prepare. Don't railroad. If the PCs do something really unexpected, roll with it.
-Epic Fail — on how to turn failure into entertainment for the players anyway. (Hunt: without DMus ex machina to undo their failure, of course.)
-The Villains Fault — more advice on running villains effectively
-T'wit — on pacing and contraction and helping the players stay on track without dragging them to the game.
-Lies My DM Told Me — more great advice on running NPCs
-C'est La Vie — PC death (note: the assumptions are for modern D&D where resurrection magic is relatively commonplace.)
-The Invisible Railroad — it's not as bad as it sounds...
-The Covenant of the Arcs — building campaigns around "story arcs" and NPC motivations rather than hex or site based exploration or module running and railroads
-Setups and Payoffs — general GMing advice.
-Love Letter to Ed Greenwood — not as cringey as it sounds (although Perkins is also Canadian...) More about NPCs, really.
-3DNPC — effective NPCs. Echoes some Ray Winninger advice, actually—specifically his Second Rule of Dungeoncraft
-Boo Hoo — on challenging the PCs. A lot.
-Catapult — on risk taking as players, and how to manage as GM
-Lloyd the Beholder — on humor
-Event Horizon — on session planning
-Behind Every Good DM, Part 1 — player feedback
-Behind Every Good DM, Part 2 — more player feedback
-Riot Acts — on the three act encounter. Highly recommended. Brilliant stuff.
-My Campaign Has Issues — on political and social issues that are "real life"
-Player vs. Player — a specific kind of challenge for players. Recommended too.
-Real Complicated — on planning pre-arranged complications, as well as taking advantage of opportunities for unplanned complications, that make the campaign more interesting.
-Slave to the Rules — on rewarding PCs for making bold decisions, even if the rules "should" make such bold decisions tactically or strategically unsound. This is less an issue with a rules lite game as I prefer.
-Unfinished Business — on PCs leaving behind certain plot hooks unresolved to pursue something else, and what to do to make that work out.
-Shiny New Thing — when another idea crowds out your love for your current campaign and tempts you to divorce it, or have an RPG affair.
-The Circus Is In Town — on having a bizarre collection of characters that look nothing like the population of the setting in which they are adventuring.
-Stephen King's Third Eye — advice from a popular writer on descriptions
-The Storytelling King — lots of DMing advice borrowed from the literary advice of Stephen King (and I will note: although Perkins is obviously a big fan of King; I am not. But the advice is still mostly sound.)
-I Am Devastatorz Megabomb, Destroyer of Worlds! — when the PCs have a powerful artifact that changes their interaction with the campaign in potentially unpredictable (or at least unpredicted) ways.
-A Lesson in Mediocrity — on those sessions when you're just not on your A-game for whatever reason as GM.
-Waxing Gygaxian — dungeons for a campaign and GM that doesn't normally use dungeons (interesting for me, at least, since I absolutely fit that description.)
-Never Surrender — when PCs fight to the death... and die. A lot of advice around GM/player trust as well.
-Cuts and Splinters — when the party splits, and a technique to manage without losing the attention of the guys not in play at the moment.
-Acererak's Apprentice — some dungeon concept ideas submitted by readers
-Kitchen Sinks and Frying Pans — encounter balance, and how it's been bad for the game
-Ice Capades — on structuring a session for best entertainment value to the players
-Know-It-All — on the value of an NPC that the PCs can trust to give them good information that helps the game progress when needed.
-Triple Threat — on GM skills, but especially the importance of improvisation
-Demigenius — on borrowing and kitbashing ideas to create something that feels fresh and original—without necessarily being really cleverly innovative or truly new.
-Extra Ordinary — on the uses of truly ordinary NPCs as "extras" to flesh out the campaign setting as one populated by things other than antagonists, patrons, treasures and monsters.
-Stan! Down — guest post by a player who died after getting himself into an implausible pickle, but how it was an organic and predictable (and predicted) outcome from choices that his player made over the course of many, many sessions of play, and how it's not good for GM's to save PCs from themselves (or their players.)
-The Moral Compass — on dealing with a group of anti-heroes, or even outright villainous player characters.
-Whedonism — (I also consider Joss Whedon to be vastly over-rated as a "geek icon." Plus, he's a sexual predator and psychopath, as has been recently revealed. But the advice is good, regardless of how it comes to us.) On challenging the players' expectations and surprising them.
-A Suite Alternative — a detailed rules-related article that only applies if you're using highly complex and complicated game systems (like 4e, in this case) but your style isn't really suited to that type of game. I don't know why he wouldn't just change systems instead, but it is what it is.
-Die, DM, Die! — more complicated rules specific advice—this is all completely irrelevant for a player of old skool, OD&D or B/X level complexity games.
-What's My Motivation? — on working with the players to flesh out their characters and their connection to the setting.
-The Well — on dealing with long-campaign fatigue, on dealing with interesting (and unexpected) PC choices, etc. Maybe a bit all over, but this one is really interesting to me.
-The End Is Nigh — on wrapping up long-running, complicated campaigns. Highly recommended column!
-From Jose Chung — using pacing and structural elements from TV shows to improve the development of the session; treating a session as something equivalent to an episode of a complicated show (in this case, The X-Files.)
-Old School — an interesting discussion on the exact same sentiment that I express about myself as "I'm not old school, but I am old-fashioned." Plus, some cringey name-dropped of perennial geek culture Fake Celebrities and all-around shameless betas Wil Wheaton and Ed Greenwood. Luckily, that's a minor part of the column. Blech.
-I Got Your Back — using history to inspire NPCs and plot hooks. Coupled with a spectacularly misinformed and "spun" narrative about Sir Richard Owen as a devious supervillain and Gideon Mantell as a poor, downtrodden tragedy. Nobody who's ever read a dinosaur book or seen a dinosaur documentary in the last thirty years should say that they've never heard of Gideon Mantell, fer cryin' out loud!
-Trust Gnome One — on player vs. player conflict (or more accurately, on PC vs. PC conflict, and how to make sure that it isn't actually player vs. player conflict.) Recommended.
-Leap Year — an experiment in advancing time one year after an extended period (4-5 weeks) of being unable to meet. Advantages and disadvantages of doing something like this.
-By The Nose — as you might guess from the title, this is on "when to nudge the players." Even the most self-motivated players will occasionally stall, due to confusion, feeling that they've gone into a dead end, etc. in the type of game that I prefer to run. While it's not to be encouraged, helping them out occasionally has to be a tool in the GM's toolbox.
-Necessary Evil — on using plot devices successfully.
-Death-Defying D&D — another post where Perkins has to wrassle with the system not doing what he wants it to do. Normally, I'd say these can be more or less skipped, but as it happens, there's some advice that is good here, even if you're sharp enough to either fix or replace systems that don't do what you want them to.
-Goldfingers — on tinkering with the rules; kitbashing elements in from other editions (or other games) mostly. Fer instance; I picked up Action Points from d20 Modern (and then modified them significantly), Healing Surges from 4e, although I borrowed the concept rather than the specific rules, and Minions (also from 4e) and then grafted it into m20, which was a brusque restructuring and condensation of d20.
-Acts I, II, and III — on using the famous three act structure at the session level.
-Spin the Cliché — on adding twists to well-worn and well-known elements of the game so that they feel fresh and interesting.
-The Third Rule — trust issues with NPCs. I gave some similar advice long ago here as well.
-Gang Aft Agley — sometimes the PCs do something so clever that they basically circumvent your entire adventure. It's OK. Think of it like when Indiana Jones shot that swordsman rather than having a big, physical fight scene with him. Let them enjoy their little victory... for a time....
-Sudden Death — I'm not sure I can summarize what this is "about" in terms of GMing advice, but it's a great campaign story that can ring helpful in indirect ways easily enough. I also really like the notion of an "epilogue" session after the game itself has ended; especially if it ended, as it did here, with a tragic yet noble sacrifice; a Pyrrhic victory over the god of Undeath himself. Recommended.
-All Around the Campfire — a bit of a rambly column comparing D&D to the grand oral storytelling tradition.
-Lego My Ego — on common GM failings and how to avoid them.
-Humpty Dumpty Conundrum — on using your notes to prompt interesting twists on past events when your current events wind down and you feel stuck. Recommended.
-Yippy Ki-Yay In D Minor — On the ways in which villainous organizations can be superior to villainous individuals—or at least offer things that the latter does not.
-Dial M for Melora — on using divine intervention as a play aid, and not a cheat.
-Unflappable — on GMing style, and rolling with the punches.
-The Old DM and the Sea — on learning lessons from various systems, and retrospective on 1st through 4th editions (at the time of its writing, 5e was in development.)
-Let The Conversation Begin — dialogue is the lifeblood of any interesting NPC, but it can't really be planned ahead of time effectively. This column gives four archetypes to facilitate helping you improvise interesting dialogue.
-Best Supporting Character — some players naturally gravitate to a "leadership" role in the social dynamic of the gaming table, and become the "stars" of the show, while others will tend to fall into a slightly more passive supporting character role. This is perfectly fine, as that usually fits the personality of the player. But be aware of it, and pay keen attention the dynamic, and make sure all of your players are having fun, if you want to be successful as GM.
-Ulterior Motives — on creating NPCs that drive intrigue. It's more of showing rather than telling, and although there's some good advice there, you'll still be on your own without too much of a road-map when all is said and done.
-Where's the Love? — a brief flirtation (no pun intended) on the topic of romance in-game between characters. This could have been really cringey, but luckily, Chris Perkins sees the issue as one that only rarely can be successful, and he's never really tried it.
-A World Worth Saving — make NPCs likable and competent enough that the players don't get sick of them and the whole setting, not caring to even save it when it's facing threats.
-Master of Suspense — on using suspense effectively. Also, an example of an interesting epilogue for a group that made a heroic sacrifice; TPK to save the world. Fun read.
-Make It Big — on boldness as a GM—make stuff memorable. Great read. I'm reminded of my own DEMONS IN THE MIST game, which in many ways was my most memorable; mostly because I wasn't afraid to do anything that seemed fun, even if it was well-beyond what staid, serious, Tolkien-loving D&D players would have applauded. (ed. This is the game I've made a few references to that Ovinomancer was in.)
-Where To Begin — the final column; Perkins talks about starting over. Echoes of Ray Winninger's "campaign hook" advice echo here. It's a short post, but includes a "campaign bible" for the next campaign he was to run using (presumably) 5e.
