Gear design is a rather complicated topic as the tooth profile is highly important to a good gear. There are add on applications such as GearTrax from Camnetics (http://www.camnetics.com/) that will design the correct tooth profile based on your material, speed, and load inputs. If you want to do this by hand, perform a search on the internet for gear tooth design.
Thanks for the info. My academic license does not come with the Gear Designer add-on. This is the reason why I wanted to create a gear from scracth. I found this video on youtube https://www.youtube.com/watch?v=NQhaw5tfqk0 very helpful.
If you are creating them from scratch and want to generate the involute curve, check out this video on creating it. It shows the graphical technique. Unfortunately they're using an off-brand of software.
The technique will be the same regardless of CAD sytem. What he's doing is sketching the process of "unwinding a string" from around a circle to generate the curve. There are some other videos for generating the curve but this one seemed the most direct.