Review: Kensington Wireless Presenter with Laser Pointer
tl;dr: Besides practice, there's nothing else that will help your presentation more than a rock-solid, handy, simple remote. And this one shoots out LASER BEAMS!
I've been giving presentations here and there for the past few years, and in the past, I've been tethered to my computer as I've needed to present slides, play videos in slideshows, and generally control things.
(Embellished with my little 'property of' sticker.)