Simple presentations are the most effective. Avoid natty backgrounds, daft fonts and jarring transitions between pages.
Nice clean pages, white or very pale background with black or very dark font – Arial, Tahoma, Calibri are all nice readable fonts that look good and perhaps Franklin Gothic and similar.
Bullet point the text and read from prepared notes, not the presentation. The slides should merely summarise the content and not be the content – otherwise you may as well sit back and let people read the stuff themselves.
10-15 slides max, with up to 5 bullets or 1 chart on each (some leaway here depending on the situation.
Do not try a Star Wars theme.
Do not subject your audience to death by Powerpoint.
My litmus test is can you do the presentation without Powerpoint and have it be almost if not as effective. If yes you have nailed it, if not revisit.
I prefer to present without Powerpoint altogether but it is sometimes expected and can be useful when presenting data etc.
Make sure all charts, tables, graphics, writing etc are readable. No point inserting some god awful, highly complex Excel table in as noone will be able to read it never mind make sense of it.
Cheers
Danny B