Learn as much as you can about drafting tactics. Unless you're planning to do time trials or extremely hilly races, drafting will dictate the flow of the race.

Unlike running, where you'll generally settle into a pace which you can sustain for the distance, in cycling you'll spend quite a bit of the time at a considerably submaximal pace, with many hard anaerobic surges mixed in.

If you get dropped (i.e., you get gapped from the pack) on a flat road, you'll generally not be able to catch back on, because riding in the pack's draft is so much more efficient than trying to break the wind yourself. (The pack will have a continuous supply of fresh aggressive riders at the front keeping the speed up).

As you learn about drafting, also get comfortable riding in a group. Unless you're a natural, you'll feel very nervous initially - this will make you expend more energy than you need to in the group, meaning you'll probably get dropped faster. Work on becoming relaxed in the group, and understanding the dynamics of riding in the group (e.g., "protect" your front wheel, relax your arms, don't brake unless absolutely necessary).

The best way to get all this experience is to find a racing-oriented cycling club. They should be able to provide mentoring, and you'll probably be able to meet other novices to measure yourself against. The experienced riders on group rides will be able to tell you whether you're "ready" for racing or not, and what areas of your riding to focus on.