1. They check very often for open trackers.
2. They always buffer their accounts, have a lot of seedboxes.
3. They always check the buyers section - to sell their invites/accounts.
4. They always check the secondary/premium sellers section for resell opportunities.
5. They always check the trade section for good deals and resell them.
6. To sum it all up : they create/get as many accounts and invites as possible and sell them.
7. Some make giveaways, to increase their reputation on the forum, that will give them higher chances to be picked by buyers and more trust in them, also giveaways make torrentinvites.org a bigger forum (people bring their friends).
8. Some try their best to design their thread, make it look as good as they can, to bring more buyers.
9. Some advertise torrentinvites.org on other websites, to increase the userbase of torrentinvites.org that makes them have more buyers aswell.

You can add whatever you think sellers do in this thread, to help other sellers become better sellers, and to make the buyers understand what sellers do exactly.

There are no limits to how many accounts/invites a seller can have.
Some may only have 1-20 accounts, some have 20-500, others have 500-2000, maybe some have even more on different trackers ofcourse.

There is no doubt next time torrentleech.org is open I will make 1000 accounts or more if I can instead of just 50 that I managed last time, hehe.