That was pretty cool, I was going to link some basic tutorials but I see you know your way around AE already
I don't know if there's any rule of the thumb in making visuals, I'm pretty sure it's just all about the matter of taste and personal style. I usually just start messing around until I get an idea of something that could look good on the screen. It might be a good idea to keep things simple and clean as you can always add more layers and effects in the VJ software. Repeatitive animations on some parameters like size, position and some fx work nicely when the clip is synched to BPM and while making the animation loop perfectly might be some hassle in some cases, it really is worth the trouble in my opinion.
