This is a fiddly project and you should be prepared to adjust and tweak as you go. I did not go into a ton of detail as this would become a 100 slide instructable. I will however add little tips that helped me.
I made it at the TechShop in San Jose CA.
Step 1: Templates
I went with a planetary gearset design. I bought the template from here: http://www.mkdrafting.com/buyropeplans.html
Print out the templates and spray mount them on your 3/4 stock.
Step 2: Planet Gear
Cut it out with a scroll saw. Take your time and cut as accurately as possible. Poorly cut teeth will lead to meshing issues.
Drill out the center hole with a 1/4 drill bit and drill press. You can use a hand drill but make sure you are drilling at a 90 degree angle to the gear. You do not want to drill off axis or on an angle.
TIP: Use a fine scroll saw blade 20T or higher. It will make for much smoother cuts.