Check with the guys from DICE and Healthy Habits and see if they do any weekly cross practices. I know here in Cedar Rapids we have them Tuesday and Thursday nights at our on park and have a guy that brings barriers he made up for dismounting and remounting practice, and he have a huge stair set we run up. Best advice I can give is to try your first race, and see where you need to improve and go from there, go out to a local park and ride around on grass for an hour, find some off-camber turns and take them faster each time. Also dismounts and remounts are key to not losing time, once you do them often it will look like this that is me from Psyclofest last year in the Quad Cities and here it is in video form http://www.youtube.com/watch?v=A0Xn3WASEW4