Better quality releases and more active users with much less leeches as they get thrown out.
Though there are many site admins with some complex here too.. your experience can vary.

And of course you need to contribute to the community, most trackers will grant you buffer for both uploading and keeping the torrent running. You want something, then you have to give back.
If the tracker doesnt give possebilities to build your buffer in multiple ways, other than just uploading, its usually a shit tracker.
And some are just super hard to impossible to get into. Start small, wait for open signups or just go to new trackers, they might get bigger over time.
Dont publicly beg for invites, you can humiliate yourself in private chats if you are into that.