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.

I do use private trackers but only if I can't find something on public trackers

id like to get into one, I have good seed ratios, just hard to know where to start

I've been using private trackers since demonoid. Maybe I'm just a different generation, but I enjoy sharing stuff from my local library on private trackers. Torrents rarely fully die on private trackers. People will generally reseed if they have the ability. I can quality shop, and get things that are generally harder to find/request things that I can't find anywhere.