I’m DM a D&D campaign these days, and have campaigned some more freeform one-shots. I really love doing this, and am learning a lot about this. Here’s some things I learned, collected:
DM screen
I find the default DM screen quite useless, and the others I’ve tried also haven’t been very useful. Focus on what you’re finding yourself look up most, or things you feel like you’re missing from core/online materials.
For me, that’s skills and costs.
Skills with descriptions because sometimes people want to do something weird. When I have to decide whether it’s Sleight of Hand or Acrobatics, it’s very useful to have a list of descriptions.
Costs for some range of goods and services: D&D’s economy is real strange. While prices don’t actually matter too much, you do want to stay a bit grounded. A beer shouldn’t cost 2 here and 20 in the next village. Rewards should feel worth the task, but can also not be too large.
Don’t forget to take…
Stat blocks stat blocks stat blocks. Trust me. Print them out. It sucks looking them up constantly and having to go back and forth between them. Your PCs will try to convince a random guy on the street that his mom is a dragon, and you need to know what his Wisdom save is.
Print out copies of your PC’s character sheets. They don’t have to be perfect and all-encompassing, but make sure that the scores and skills are right.
Maps
I tried various versions, like theatre of the mind, bringing an second monitor, and drawing a map on a grid. So far, I prefer drawing out the map.
Usually, I’ll scour the internet for a nice (black and white) map of a location with the vibe I’m looking for. I then edit that to put creature locations and room names on it, and print out both versions. We then draw out the rooms on a rollable grid with wet-erase markers.
NPCs
I love randomnpcgenerator.com. For planned NPCs I use its output as inspirational, and even for random NPCs that come up during play I often cut a lot of the characteristics.
For a while, I tried creating visuals from the NPCs but I don’t find it super helpful. Some identifying characteristics and a general vibe are enough to describe a person. For creatures I still find the provided images useful, because how am I suppose to describe what a fomorian looks like?