Last year was my first season racing cyclocross on an actual cyclocross bike (two years ago I used my mountain bike). In case you didn't know, cyclocross races are kind of like an obstacle course for bikes. There are barriers and stairs and hills that require you to jump off the bike, run through/over the obstacle, and then jump back on. Races last 45min to an hour and do multiple laps of a fairly short track. You don't really ever get to coast or relax like in other forms of racing.
What that means is that you had better be in good shape with some interval work, know how to corner well and conserve momentum, practice your mounts and dismounts, learn to bunny hop, and get some good tires.
