There are a few things I will suggest to someone who is more familiar with pre-3rd edition versions of the game.
You are right about the DM screen being very useful. However, you may want to re-read the sections on Bull Rush (PHB 287), Grab / Escape (PHB 290 and 288), Opportunity Attacks (PHB 290) Delay (PHB 288) and Readied Actions (PHB 291). Of those elements, Opportunity Attacks will come up most often. Readied Actions and Delayed Actions are potentially very useful to a DM if you want to wait for one monster to get into a better position to attack, or if you want to pincushion a character as he enters a room.
Players and DMs will forget to do the following:
- Apply ongoing damage at the start of a character or monsters turn
- Make saves vs ongoing effects at the end of a monsters turn
- Keep track of who is marked by your PC's.
As a DM, I tend to forget to apply the -2 penalty for being marked. Players and DM's can forget to apply the ongoing damage. For things like Marked, and Warlocks curse, have the player who triggered them do the book keeping.
If you are using a published module, be aware that WotC likes to use a few monsters of a higher level then the players as opposed to larger numbers of monsters at the same level. The fights will be survivable, but it can lead to fights that take longer then they should due to the monsters a bit too durable. You may have noticed many posts about Grind. This problem is highly subjective, and how often it shows up varies from one group to the next. If you think a fight is taking too long, just do whatever you think is necessary to speed things along (quietly cut HP, or just run away / surrender).
Skill Challenges are a great new idea for 4th Edition that you may want to adapt to your regular games. However, the pre-errata implementation was flawed. If you want to run one, make sure you are using the errata for skill DC's. Here are 3 tips for skill challenges to avoid it turning into just a series of rolls.
- Decide on a worthwhile Reward: This can be a bonus to hit or def until the next encounter or next extended rest. Treasure is also possible.
- Decide on a worthwhile punishment: Skill challenges should not roadblock an adventure due to a single failed roll. If they do fail, you should incur a real cost. This could be Healing surges, penalties to hit or def for the next encounter, money or whatever else seems reasonable.
- Do not let 1 player make every roll: You want to engage the entire party.
- Do not let 1 skill be used for every roll: Same problem as above.
- Permit players to gain a success for non skill checks: An applicable use of a ritual or just good role playing should be encouraged here too.
- Be flexible on the resolution Mechanic: The 3 strikes model is workable, but not always ideal. Any reasonable mix of successes before failure, and any reasonable spread should work. I like doing 'every player gets a penalty for every 2 failures', or 'Every player suffers a +X attack vs Fort for 1d6 damage for each failure, no go make 5 checks.'
If you need to improvise a mechanical effect (a skill DC, a non standard attack to inflict damage, etc), use page 42 of the DMG.
END COMMUNICATION