Main abbreviations you guys use please :)

[Omanes Alexandrapolites]

I would link to a wiki page, but it contains bad langage, so I sadly cannot, or at least not without breaking the forum rules. Sorry. However, from what I know:

AFAIK — As far as I know
BTW — By the way
Bump — When somebody posts in a thread to bring it back up to the top of the forum page and get it noticed.
Spam — Posting, which often makes no sense, just to increase post-count. Most posts of this nature include the phrase "+1" to indicate the level of which their post count has increased by.
AoR (a.k.a ZoR) — Area/Zone of recruitment, A feature in many modifications, and in the games M:TW and R:TW, which restricts certain units to be trained in certain regions. For example, Swiss Pikemen can only be trained in the province of Switzerland or Spartan Hoplites only being available in Sparta and Syracuse.
PBM (a.k.a PBeM)— Play by (e-mail) campaign. A nice explanation of this can be found here.

Hope this helps, cheers!