I took the following note during a colleague's presentation the other day:
Use slides to support your voice-over, not the other way around.
Going through my notes today, this dumb little remark made me pause and think because it's too apt.
The audience is listening to your narration first and foremost, whatever is shown on the screen is supporting material. If you don't follow this, your slide deck becomes too busy and complex, and you'll end up trying to explain whatever is shown, rather than focusing on what your point is.
I'm no great presenter, but I feel fairly confident with this advice.
Send me a note if it ever helps or inspires you.