Your first decision is which class you fancy racing in.
After you have done that, you need to have an idea of/calculate your budget and plans. i.e. if you plan just to hit it for one season, you can go a bit mad financially, if you are planning to do it for the foreseeable future, maxing out your credit cards on day1 probably isn’t the best idea!!
You could get yourself to a meet and walk round the paddock asking questions. This is a great idea in theory, but to be honest, you would need to pick your time and person to do this. People get pretty wrapped up in what they are doing at race meets.
Visit
http://www.motoforum.net/ that is a forum used by race clubs, put you post on there and ask questions. Being a forum, you are obviously not going to risk accidentally interrupting someone when they are having a race crisis like you might at a meet!!
You might want to get some idea of your pace too. What group were you in at the trackday?? and where would you say you were?? If you are comfortable in a fast group, then you are probably ready to think about racing, if you are wobbling round in the beginners or inters, it might be a better idea to get more tracktime first.
Many trackdays frown on unofficial timing, but if you do a ‘Paceday’ run by hottrax then you get official timings. Although there is more to racecraft than simply being able to put in a hot lap, laptimes are your best indicator of you readiness.