One step to a perfect presentation

#1 piece of advice for all presenters: know your presentation by heart.

I've been to four different conferences in the past three weeks. I've seen a lot of presentations - a few good and many that could use some help. All the presentations I saw could be fixed with one best practice:

Know how to tell your story without your slides. 

I recommend writing your talk first. Practice it. Then figure out what the major points are. Practice again with just one main point on a slide. Then fill out your slides. Then practice again without slides. Your presentation will be a 100% better, you'll survive computer failures and you won't commit many errors like looking at your slides, reading your slides,  ... or the worst, not being able to give your presentation when the projector or your computer won't work.