Number/label your slides---makes it easier to reference
Look at your audience
Be animated
Repeat any question or comment... it makes it so that everyone can hear it, makes sure you understand it, and gives you time to think
What is your goal? To teach them the hardest parts of your research? No, intrigue them enough that they want to know more, or perhaps enlighten and entertain for 15 minutes.
Practice gives you an idea of what slide is coming next, and helps make your presentation flow