Tactics:
Use the most unfair weapon. If people complain they can blame the host.
Typekill. Their fault for typing in the middle of a fight.
The default rocket launcher is a 1 hit kill weapon. Use it unless there's a 1-3 hit kill machine gun, or an explosive weapon with a wider range still killing in 1 hit. These would be the most unfair weapons.
Spawnkill. If it's a normal DM, blame the host for crappy spawns, or the person for not shooting fast enough. If it's a TDM, they can only blame their team for not being good enough.
Jetpack DMs always suck. Don't join them.
In CityRPs, events are your best weapon. You'll probably be kicked/banned though. Oh well CityRPs suck.