Were there raisers? How many are in the pot now? Can you bluff these players or will they cal down with any pair? Have you had showdowns where you drew 2 and only shown one pair, making it obvious you are holding a kicker? Or, the opposite, when you have shown down after throwing 2 was it a set? See, this game is a little more complicated that most people believe.
Generally, I throw 3 with a pair since sets are more likely to win then 2 pair plus even if you throw 3 you may still get 2 pair. I usually only save a kicker if I plan on bluffing after the draw representing a set or better.
I believe your odds
of "improving" your pair is better throwing 3 then keeping a kicker and throwing 2. But like everything in poker nothing is hard and fast, it's good to mix up your game andf occasionally keep a kicker but generally draw 3.