I would say...
0. Read and learn all you can about private trackers, there are a lot of info on google ( ratios / user classes / seeding / all related to torrenting )
1. Find a tracker you like ( type of content ), mostly a small/new one.
2. Look for open sign ups/invites, make your way through the different user classes, read FAQs and Rules
3. Have fun and make friends! Eventually you'll get what you're looking for.