il be informative for once: press P ingame to join a # battallion, once your in one you can press F1 to place a flag, hold rapidly press F1 to drag the flag over the map and release to place, if u face your feet at release the flag will appear on you.
This. (with small correction)
One important thing to remember: when carrying the flag,
always remember to release the flag before you respawn. Else it gets stuck. Let me explain in more detail:
When you carry a flag (join a battalion by pressing P and look at your feet and press F1 to start carrying that flag), other players are not able to control your flag until you place it on the floor somewhere (by looking there and pressing F1). If you die carrying the flag, the game still has it registered as being carried and the flag gets stuck and cannot be reused next round. When the map changes, this gets fixed of course. But it's nice to be able to reuse the flag the next round. So remember: press F1 to release the flag when carrying it. This works even after you die.
So if you die carrying a flag, tap F1, else flag is stuck. Wrote a guide about tactics ages ago, also covers some basics about flags iirc:
http://forum.c-rpg.net/index.php/topic,27.0.html