I kind of decided that I wanted a coach after speaking with my brother and other cycling friends who said that the single biggest "upgrade" you can make to your cycling is getting a coach. Since I was already in USA Cycling, I started by searching on their list for someone who was somewhat close by:
http://usacycling.org/news/user/story.php?id=95
After I found a couple of people, I asked them questions like: 1.) What is their experience? 2.) How much do they cost? 3.) What comes with their coaching services? 4.) How available are they for talking on the phone, meeting, internet chat? After all of those things, the decision kind of made itself.
Since then, our coaching relationship is purely done over the phone and via email. I receive workouts from him electronically and I send him my workout files from my Garmin after each day. After races, I'll either email him a brief report if it was not that important of a race or we'll talk on the phone to analyze the race, strategy, pros/cons, etc. So far, that has worked out very well for me and keeps me motivated. My coach is a Cat 1 racer himself and has a ton of experience.
Other coaching services out there such as Carmichael Training and Plan2Peak are great from what I hear as well, however, probably a little more expensive than the coaching that I am receiving. The biggest thing that I can say that coaching does is it provides someone who you can talk to analyze and meter your progress and ACCOUNTABILITY. If I bag a ride on a rainy day, I feel bad about it or feel embarrassed that I have to report that to my coach. Good luck, stay committed, and your results will come!