The NCAA is currently working on a formal system to develop NCAA Umpires. So, right now there is not a "Standard" way. However, the U.S. is broken up into thirds with a Umpire co-ordinator responsible for that area.
Go to
http://www.cactusumpires.com and click on College Stuff. The co-ordinators are listed. Once you find out who is in charge of your area, I would e-mail them asking for their advice. Also find out who works college ball in your area and ask them.
Many assigners(at least in our area)use fall tournaments as a way to evaluate new umpires. If you make the cut, then they will assign you to some Jr. College/Div 3/Div 2 games for a season and then re-evaluate you the following fall.
To be honest, we happened to be in the right place at the right time with the right person. We were working a Little League 12 year-old tournament and a member of our crew was the assigner for a couple of college conferences(We had no idea at the time who he was). Anyway, after working with us for the weekend he asked if we would be interested in working some softball. We worked a couple of fall tournaments, received good ratings, and the rest is history.