Red (music) and MAM (audiobooks) have open interviews and have good invite forums that can get you into other trackers. Both are best in class for their categories. Starting with RED truly is a trial by fire with the hardest ratio economy around but it is definitely the most rewarding. MAM is super friendly and easygoing but it can take a few jumps and some time to make it to the bigger trackers. Getting in a good general tracker like FileList, Torrentleech, or IPT really opens up the amount of content available to you starting out if you can find an invite, just know you generally can't make it to other trackers from them. That being said general trackers own their own can be enough to satisfy many peoples needs. Good luck with your journey, I'd be happy to help if you have any more questions.

In general the procedure is to go through recruitment forums on trackers you are already in or occasionally interviews and open signups when starting out. For BTN specifically they have not opened recruitment in a long time and invites are few and far between. So right now you have to be get lucky and befriend someone with a very high ranking and is stacked with bp that can get you an invite.

You've posted this twice in the same thread. Nobody likes an invite beggar.