Yep, done a bit of that. Here's some tips I can offer:
A good, sharp knife is essential, as is a good cutting mat. Pen-grip knives give you better cutting control than utility knives, but with enough practice, you can get similar results with either one.
If you're printing colour and patterns on the paper, use paper that can hold the colour well. Otherwise the ink will run when you get the slightest bit of moisture on (eg glue from the back) and you get streaky patterns.

Better yet, just fold everything from white paper first, and then paint on the colours yourself!
The nozzles of glue bottles are usually too big and allow too much glue to flow. Using a stick will allow you to put just the right amount of glue on. Just slice off an ice cream stick or a chopstick at an angle to get a sharp wedge, then use this end to apply the glue.
Here's a really cool model that I found just recently:
http://www.instructables.com/id/Walking ... h_Warrior/
Gonna see if I can just keep the mechanism and have interchangeable mechs on it.
