The only favor my fiancee gets is a cuddle if I hideously slaughter her character. Those Age of Worms adventures are deadly.
I try to avoid favor by looking at characters and having 10 minutes or so where each character shines brightly. It makes everyone have something to congratulate themselves about, basically.
A fighter with great cleave will slaughter a bunch of 4 hit point lackeys. A swashbuckler will duel with another swashbuckler while swinging from chandeliers on the roof. A cleric/paladin will explore corruption within his church and interact with his deities code of behaviour. A monk will chase people across rooftops and a rogue will have things to do that only his skill list can accomplish.
If I work with it like that I avoid blatant favoritism basically. Overall theres been only a little tension with another couple who were fighting at the time, but it wasn't really an issue.