Small pairs: Limp or call a raise that is less than 5% of yours and your opponents stack (whichever is smallest), and then No Set No Bet
Medium pairs (99-JJ): Same as small pairs only you'll sometimes have an overpair. But if there's even ONE card above yours on the board, don't put ANY money in against more than one player. If you call a raise with it, use the No Set No Bet rule to be on the safe side.
Big pairs: Always raise and re-raise with them preflop. As long as there's no Ace on the board, bet. If there's an Ace on the board you need a set to bet. If you raise QQ and get 3 callers, then an Ace flops, do yourself a favor and check/fold.
If you never bet unless you have a set or an overpair, and are willing to lay down an overpair from time to time, you'll make money from your pairs. It's not any more complicated than that.
