I am trying to figure out a better strategy with regards to playing my pocket pairs in no limit cash games.  Specifically, it's the smaller pocket pairs I am having the most trouble playing profitably.  I've already abandoned playing them altogether from early position in 9 man and gave up playing 22 through 44 in first position in 6 max unless there is a complete fish at the table. 

I was wondering what the community thought was the most profitable way to play small pocket pairs, both in position and out of position.  Is there a specific size stack a person needs to have to make set mining a good idea (I generally use the rule that if the person has 15 times the bet he makes behind I can try to set mine profitably, I use 20 times the bet for suited connectors . . .) Is this too conservative or should I be 3 betting these pairs to introduce some fold equity into the equation?

Any advice is welcome, thanks.