Every year on January 1st, for over 15 years, my group of friends have been doing a "New Year's RPG session". I've played and DMmed my fair share of 3E, 3.5E, and D20 Modern, but I've stopped playing about 4 years ago. My friends have kept on playing and now prefer 5th edition.
This January 1st, I volunteered to DM a 5th edition "one shot". My question is simple (though possibly a tad bit broad):
What are the very very basic pieces of rules I should know about when DMming 5th edition?
To make it less broad, assume:
- Someone reasonably experienced at DMming (including "winging it" if needed)
- A fully fleshed out, custom, home-brew one-shot story ready to go (backgrounds, maps, etc all taken care of by me)
- Helpful, cooperative players, several of whom have DMmed 5th edition themselves
- Near-zero risk of power playing, rule abuse, and the like from players
- Level 5 characters
- Adventure with intended mix of combat, skills, puzzles, and role playing
It's hard to "know what you don't know", but judging from earlier editions, I'm particularly worried about things like these from 3e and 3.5e:
- Things like passive abilities (like ones to detect secret doors) I should know about
- Certain skills being "opposed", where the DM should roll for a player, hiding the result
- What reasonable DCs are (e.g. what a reasonable AC would be, or a reasonable break DC for a door)
- Combat rules that you'd really want to read up on, ahead of time (e.g. Grapple was so nontrivial, that if you have a grappling enemy in the story you'd better read up in 3.5e)
My players have all the books, and they've also provided me with the 5th ed. SRD (pdf), but I have neither time nor interest to read through it all (right now, at least).