How do I learn 3D modelling?

I have horrible 2D drawing ability, yet I would like to try learning 3D modelling.  What are some good prerequisites for this?  What kind of people usually are good at it?  What classes would you take if there were college courses related to it?  I would like to become proficient in 3DsMax, Maya, or whatever else comes out, but I don't know how long it will take to know whether I have potential or whether it's not my thing.

3Ds Max comes with a lot of tutorials that are pretty helpful. After that it's just practice and not sucking.

just don't.  more trouble than it's worth, trust me.