Subtle things I've noticed
LOVE, LOVE, LOVE this game... Here are a few things that struck me as useful:
1) There is a max percentage you can repair things based on your Repair skill. It seems to be higher if you fix a low % item with a high % item instead of the opposite. So, fixing a 10% with a 60% is better when maxing out.
2) If a lock can be picked OR hacked, you can still hack the computer after you pick the lock for more XP. The reverse is not true.
3) You can usually disarm mines by crouch-walking up to them while keeping the cursor on the mine, even with a very low Explosives skill. The trick is to keep moving forward, as you have a very short time between the beeps and the boom. Hit the disarm key as soon as the square brackets appear.
3b) Mines make great markers in tunnels -- they glow, you can't set them off yourself, and they guard your back if you bypass doors and/or tunnel mouths.
4) PIPBoy pausing can be seriously exploited in combat. You can actually repair armor and weapons, or put on medical garb to give yourself meds more effectively. Feel free to eat 20 or so food items, while you're at it.
5) Pick up EVERYTHING. Feel free to drop the junk into the nearby trash can, but I've collected a fair number of unexpected things like skill books or energy cells that were quasi-hidden among piles of ruined books or tin cans. I also dump out any wooden boxes, pots, etc., even if they seem empty at first glance. Takes a little time, but there are some surprises. Using the flashlight also helps (hold TAB on the PC to turn it on -- took me FOREVER to figure that out 'cause I missed it in the tutorial).
6) Cars aren't the only things that explode. So do floor cleaners, and fire extinguishers. Also, mines and grenades lying around will go off, especially under flamer or missile fire. Traps can be set off by fire or even objects kicked into tripwires (by you or by others). Usually, this is not to your advantage unless you're being clever. There is one quest you can get in Megaton from Sarah Palin's twin sister where this is REALLY annoying -- you know it if you've played it.
7) Try all the custom items at least once -- there is a schematic for every category of weapon other than energy. Trust me -- sometimes it is freakin' hysterical.
8) Find the roving trader's outfit and hat -- together you get +10% to barter, which is free money. You only have to wear it when you talk to merchants, of course.
9) House tips: the Lover and Science themes for your apartment include skill books, which are a limited commodity in the game. The other themes aren't worth the caps. Also avoid the jukebox, as it does the same exact thing as your PIPBoy, i.e., plays the radio. (If you're drowning in caps, go ahead and splurge -- thievery can make that possible.) Also, don't forget to go back to your robot butler for purified water periodically. Besides the rad-free hp boost, you can also give it to beggers to counteract negative karma.
10) Things to almost always buy: schematics, house upgrades (see 9), ammo (especially the rarer types like .308 or .44 if you use the related weapons), heavily damaged armor and weapons for repairs, bobby pins. Most other things you will easily stumble across in your travels. Some things like skill books and Nuka-Cola Quantums are almost never available for sale. Why waste money buying a 75-cap fission battery when you can go out and waste a robot that will have one as loot? Hold onto pre-war money until you find something you really want, as it weighs nothing. Stimpaks are also good weightless commodities, though you don't usually want to sell them.
OK...enough with the tips.
One last thing, though. I lived in the DC area for many years, and I have to say that while the game setting is off in some very important ways, the guys at Bethesda have done a great job of getting the feel of DC down. From the hexagonal tiles in metro stations, to the view from Dupont Circle, to the placement of most things in relation to each other -- things feel right, with only a few exceptions (looking at you, Georgetown!).