Don't use the really high lethal killstreaks. I'm far from terrible, but I do play solo most of the time, and nothing annoys me more than when my teammates give up high killstreaks to the enemy. I will usually end up leaving if I keep having to deal with dogs, swarm, etc etc.
The highest lethal anyone I play with uses is usually the lightning strike.
Sometimes no lethals at all.
And for anyone wondering, i'm not talking about with a full party. I've been playing in groups of 2-4 and people still quit everygame.
"Persistence until excellence." http://www.youtube.com/user/supercoolisaac