If you lose your train of thought during your next presentation, don't sweat it. The audience will know if you get flustered and it will just make it worse. Instead, take a simple 10-second pause and people will assume it's on purpose.
Photo by Nazareth College
Over at Inc.com, they have compiled a big list of public speaking tips from Ted Talks. Seth Godin has an interesting way of making your audience think you paused on purpose:
Pause for two or three seconds and audiences assume you've lost your place; five seconds they think the pause is intentional; after ten seconds even the people texting can't help looking up.
When you start speaking again the audience naturally assumes the pause was intentional... and that you're a confident and accomplished speaker. A poor speaker abhors a vacuum; only confident speakers are secure with silence. Take one long pause to gather your thoughts and the audience will automatically give you speaker bonus points.
Check the full link for the big list -- there's some good stuff in there.