Notes are always a good idea. You have no idea how many times I've run a campaign and one of my players have remembered some obscure detail and I'm stumped. So here are a few things I've done to help me remember the small things that sometimes aren't so small.
1) Keep a spiral! Get the big highlights down, for sure, like NPCs you have to make up on the fly, spectacular fight highlights, and names of buildings you add in. Anything else you can get down is gravy. After an adventure, I always re-write my notes, whether in another spiral or on a running word document.
2) Have handy a cheat sheet of character stats. Hit points, AC and saves are a good thing to have on hand so you can fudge if you need to, (though I know Hackmaster fans always let the dice lay), or roll those sneaky attacks or saves as needed.
3) I also keep a running list of ideas or items I need to expand on. My daughter got side tracked with a disembodied voice in a ruin she wanted to "save" and named Bob, (for all those Jim Butcher fans). So I kept a note on that and brought the voice in later for some other adventure. Little things like this show the players you are paying attention and want them to have fun.
4) Cheat sheet of rules. Most system have a GM screen with the need to know rules, but if not, make your own sheet up. Simple things like DC for commonly used skills, common feats, and common battle options, (such as attacks of opportunities or attacks/spells that spawn attacks of opportunities), are good to have on hand.
Tomorrow the all important food.