So really, TBT bells are rewarded for every post you make, the longer it is the more TBT bells earned. Creating posts in certain sections like in the introductory board and the basement do not give bells for your posts. Editing your posts will deduct/vary the bells you earned in that post. You can also earn TBT bells by voting on polls. You can see all your transactions at http://www.belltreeforums.com/credits.php.
TBT bells are the virtual currency exclusively used here at the belltreeforums which can be exchanged for in-game bells, in-game items, artwork and many other things.
//e: This post earned me 5.7 Bells but editing it will deduct the amount o7