Make sure you maintain a consistent graphical language throughout your slides. Here is a thumbnail view of a section of a deck I used in recent meetings.
Here are the guidelines I used:
Dark background, white text, purple accent
Page-filling, black and white images
No capitals
Selectively bolding a word in a sentence
No slide titles in a fixed position
Every slide blends right in without, complicated graphics, and SlideMagic makes it really easy to apply this style.
SlideMagic: a platform for magical presentations. Free student plan available.