The single biggest piece of advice that I can give you is NOT to use features like animation, sounds, video clips, etc. in your PowerPoint presentation. Please. For the love of God, don't do it.
The basic principles of presentations are still the same -- your visual aids are meant to be used to augment your delivery, not distract from it or take the place of the verbal/visual message that YOU are presenting. The classic rules still apply: Use visual devices (graphics, photographs, diagrams) as the primary focus of your slides. Use words sparingly, and only to reinforce key points that you will deliver in that part of the presentation. Organize the content in a logical and easy-to-follow way.
The only exception to the "classic" rules is when the presentation is also being used as documentation -- which is, unfortunately, endemic in engineering. In that case, you have to be more verbose and detailed with your slide contents, since there is a potential audience which will not get to hear your in-person delivery. However, that can also be accomplished -- perhaps more elegantly -- with notes. And, oh yeah, I've seen animation used effectively...exactly ONCE.
Clearly, using an attractive visual style and color scheme can enhance the impact of your presentation. But most people make some <AHEM> interesting choices which actually work against what they are trying to achieve.