The following is not really a trick so much as heavily treading on someone's toes. Mostly farming an active player, with half my points and a small force, a few times in a relatively short period of time without allowing much room for recovery.
I play a video game called Guild Wars where the farming is purely business and against computer-controlled monsters, not other players. This is the first time in ages where I have played a game that involves farming other players, and I fully admit I need to get out of the guild wars farming mind frame when it comes to active players and have a care for feelings. It was only around the time, give or take, the player mentioned retaliated that the difference became clear. I know I wouldn't appreciate being constantly farmed by the same guy without stopping.
Sure, Tribal Wars is all about gaining the upper hand and rimming other players, but it can be decently done.
Edit: Oh dear, and I just had to ramble about decency in this particular thread. Just ignore me =D.