Kristen

What kind of racing do you want to do?

Well, you have motocross.. enduro, scrambles.. and various others.

They're all vastly different in where and how you race, and equipment you'll need.

Where do you ride now?

If you want to race MX then you should look around for a local track and start practicing. One advantage of MX racing is that you can always ride the track slowly. With scrambles and similar type races the course could take you over terrain that you may not be able to handle at any speed. Another advantage of MX is that you can do it solo.

If the airborne nature of MX isn't your style then I would recommend finding a local club to join. Quite the opposite of MX, a scramble or enduro can take you far away from camp and if you break down miles away having someone who will not only know you are missing but come look for you is vital. Such clubs are often affiliated with the AMA and your local district (I believe you would be in district 29). The AMA website has a list of clubs :
http://www.ama-cycle.org/clubs/index.asp

As for the type of racing:

MX is usually on a closed, maintained course. Lots of tight turns and jumps. Races are generally in "heats" and will be a number of laps around a fairly short distance. Twenty minute heats would be fairly long for a novice level race. You usually get to practice the course before race time and you can certainly see all of it ahead of time.

Scrambles are usually out over natural terrain. They may follow designated routes or if they are in an "open" area the course could be virgin terrain marked by ribbon tied to bushes. Some events allow you to practice the start (bomb run) for about the first mile but otherwise practice is not allowed. This means that over every rise or around every corner could be a surprise.

Grand Prix is a mix between MX and scramble. A common format is to run ten miles through natural terrain and then a quick pass through the MX track. A Grand Prix might have three laps around a 10 mile course.

Enduros come in two basic flavors: national and timekeeping. The national format is essentially a race except you may have some rest periods scattered through it. A time keeper involves strategy in addition to speed. A beginner level time keeping enduro can be a fairly easy ride and still be very challenging. Enduros tend to be long: 60 to 100 miles.


Rod

If you're anywhere near Augusta and want to try MX, Gordon Park has a Trail Bike class that your TTR125 would fit in.

http://georgiamxbuilders.com/Racing.html

From looking at their schedule, they are racing again Saturday 10/3. You could come to check it out, or if you are adventurous, bring your bike and race!