A PowerPoint template or color scheme with a neutral, gradient background works best for most presentations.
High contrast color schemes may be used if the room or data projector are not ideal. High contrast means that the text and background are not even close to the same hue.
Use the same background for the entire presentation.
Illustrate concepts and critters.
Suggestion: Include slides containing relevant graphics. Example: a photograph of a parasite, a map illustrating the incidence worldwide, a movie of a microscopic wet prep of the parasite, a graph of results of a study of effectiveness of diagnosis or treatments.
Try to show more personality than the podium. However, use of humor is only advised if you have some comedic talent. Injection of Far Side cartoons, etc., should apply to the topic. Long talks can be improved with these, but don't overuse them.
Involve the audience, if possible. Let their experience or expertise improve the talk. When the topic allows, using stories from your own experience improves the presentation.
Speak to the audience, not the computer or the projection screen.
Practice so that you appear at ease. Do not read talk.
Speak at a reasonable rate, not too fast or slow.
Speak clearly and audibly. Don't mumble. People sitting at the back of the room should be able to hear you.
Use the allotted presentation time effectively. Do not run short or over the allotted time.
Allow time for discussion and questions from the audience.
Don't kill trees just for the sake of having a handout.
If you have an illustration that is too complicated to project on the screen, such as an intricate algorithm, hand that out and refer to it in your talk.
Give the audience something useful like a job aid, list of abbreviations, or outline.
Board questions on the topic make a good handout.
Articles kill trees, but the seminal article on the topic is good. Short of that, a reference/resource list is good with URLs.
For some audiences such as a group of residents who don't have anything to write on, the PowerPoint 3 slides-per-page handout is good for taking notes.
Otherwise, put your presentation on Blackboard or on the web, and let the audience print out what they like in the way of a handout.