1. When one shotting, I like having people make characters in advance over pregens. Give em a few directions, and a reason for being together, and just roll the stats and check the sheets before you start. The lower lever the party is, the easier this is to do.
2. Keep it simple. You don't need half a dozen intricate plot hooks and complex NPCs. Give them one solid hook and a couple of colorful NPCs and call it good.
3. Don't be afraid to get them into the adventure. Railroading is different in a one shot than in a regular game. The players won't mind being pushed a bit, and will take mostly whatever bait is offered, so that the game can commence.
4. If you fall behind, and this is your only chance to run this game, you can always skip encounters. Glaze over nonessential exchanges, have nights pass uneventfully, nix the wandering monsters. Worst comes to worst, when there's only 20 minutes left in the session, look! That next bend in the tunnel leads right to the BBEG.
I also like to get silly in one shots. There are ridiculous things that would be irritating if played in a long term, serious game, but are funny for a short. Last one shot I played in, I was a hobbit ranger that wore a hooded cloak, and sat in a shadowy corner and smoked at every oppotunity. Good times.