I have a few rules:
1-Printscreens must be taken with the window size as small as possible. A screen shot of a 640x800 window is best to view on a projector than a 1920x1080 window. It makes all text clearer for the screen shot. After all, you don't know the resolution of the target projector.
2-My general presentation layout uses a dark image background, with large bright text, or the reverse. It depends if I am in a dark room or a lit up room for my presentation. It also makes a good contrast with screenshot contents...
3-Use large fonts and limits yourself to only a few points per slide. I have good eyes, but not everyone has.
4-Projectors have a tendency to brighten everything, and makes colors strange, unless you can fiddle with the projector settings. Don't rely too much on color accuracy.
5-Live coding sessions is bad, because users won't pay attention and you will loose time testing / compiling. Pre-make your sample projects, and only shows in your presentations the lines of code that really matters. You may have the control over the code window, but users don't know if you are going up or down, and they can quickly loose track.
6-Create more slides if you need to show more things.