Ok I think I'll throw my hat in the ring on this one as well. These are all great solutions in various forms, but I still think they lack a little clearity (no offense) Hopefully I will be able to put this all together for you and it will combine everything said thus far and become very clear.
Here are the essentials:
1. Only Ranked Matches count for kills!
2. 8 different gamertags are needed to start Ranked matches.
3. Only about 127 kills count, If you go over the kill counter resets to 0 and that includes any kills you have gotten.
4. A good sense of humor or conversation skills to keep everyone going!
Now to the difference (per se)
My groups method:
Game Type: Deathmatch (it's free for all)
MAP: Waylands Keep. (it's relatively small and provides a common kill gorund with benifits that I will explaine a little further down)
TIME LIMIT: 20 min.
2 gamers on Undead. (They will earn the kills for the match.)
6 gamers on Human side. (They will die horrible for the match.)
Undead gamers (Pick Mages, with turret ability)
Turrets will never deplete in magical energy and they will never get destroyed, UNLESS someone deals damage to them (shoot with arrow, hit with sword etc..) OR they get a richochet (Blow back damage) effect that is why it is unwise to use the Lighting turret. Instead use any other turret. and any other abilities you like. (Fireball and Firestorm so work wonders as well durring the match)
When the match begins, the two undead players will be earning the kills, head out and find the courtyard area (middle of the map) this courtyard has two sets of stairs. Both undead gamers will choose the same set of stairs (this is essential) One on one side the other on the opposite side.
Both undead gamers will set up thier turrets so that they can fire freely into the courtyard without hitting the others turret. (This is why you set up on opposites sides of the same set of stairs.)
Now for 20 minutes, the Humans, will charge recklessly into the turrets (if you want to do damage to yourselves then by all means pick mages and use the burnig finger or fireball directly at the ground or the wall to do damage to your self. (Just becareful not to over do it and kill yourself or someone nearby)
There is also a run spell that helps you move a lot faster for both mages and archers. STAY AWAY from being warriors as they are slow and harder to kill.
Using the B button the two undead gamers getting the kills will watch their scores, they should stay within 300 points of each other. Doing it this way, both undead gamers will net about between 100 - 120 kills each, keeping them both just under the reset limit, but netting them both the most kills.
This method will run 8 players thru, each netting around 120 kills and being just under 2 hours. Break it down in to mutliple sessions or just round robin till everyone is done in about 5 to 6 hours.
Sticking to the above 20 min. 300 score difference will usually keep you in check, but I'm obligated to tell you this:
20 min games can be a bit boring and It is possible that if you have a very good effective boosting group that you CAN BOTH go over the reset limit so KEEP AN EYE ON YOUR KILLS!!
We have found that a group of 8 can get very efficient at this, getting kills up to the Kill count reset limit well before the 20 min match time limit. When (not if) you get your group this good, then it is suggested to rotate the gamers doing the killing and have 4 people killing per match. Each taking 10 minutes!
Thanks go out to all those brave souls before me and the great effort and experimentation it took to find all of this info out.