Guildmembers get DKP for attendence when a raid starts and ends, in some cases even if a guildmember didn't fit in the raid but are online doing something else he gets dkp, when a boss dies everyone in the raid gets DKP, new boss kills can grant a bonus dkp sum, erratic behaviour can lead to minus dkp.
Something like that.
Then when a boss drops something needers are asked to whisper the loot/dkp overseer and the person with the most DKP gets the item.

Myself find a system without DKP where loot is given to the person that needs it the most gets it if they have a 75~% presence on raids, aka are an active raider, the best, and MainTank should also be the GM ideally since then it's not as easy for him to "lamexit", this is the case in my lvl70s guild where GM=MT but It was kinda stupid when a shaman got a new shield in ZA and a few minutes later we wiped cause the new palla tank had too much crap gear, including a shield with around 2k less armor than the one the shaman won roll on (the guild only use dkp in 25mans.)

Excuse my grammar etc.