How do you do timing on your videos? Do you record audio first and match graphics to it?
I've experimented with voice recording before, and the one mistake I discovered that I was making was in having the microphone too far away, I had to increase volume to hear my voice and that increased background noise (computer fans). This was because I was recording tutorials, and I was recording audio and video live.
I always begin with the script, record that. Then use the edited narration track as the timing reference for everything else (Occasionally I'll make small timing changes later to facilitate some visual treatment I want to do).