Best bet. Go to a racing website WERA, CRMA, CCS and read through the various threads already started. Or find a track day near you adn swing by and just hang out. Many track day people also race and a lot are willing to help.
But basically, decide which racing org you want into, go to a race school to get a license, read the race manual, and show up.
The best bet, hang out/search at the racing websites.