To borrow a line from Ed Miller, middle to low pocket pairs are "binary hands"... That is to say, the flop either makes your hand or it doesn't. Rarely will you flop a draw with this kind of starting hand. That's nice because you can make a good bit of money on a flopped set (or better) but more importantly because you're going to save money by not calling down draws. If you don't hit, lay 'em down and move on.
As a quick side note, I wanted to illustrate why I say limiting your losses is more important than maximizing wins, at least at the micro-stakes online games... Because it's a lot harder to do. Large bets are far too common at these tables and losing pots you've fed to the river can get very expensive to do with any kind of regularity. If you get really good at limiting your losses when your luck is running bad, you've already taken a large step toward long term profitability. Don't get me wrong, though, you should never use this advice as a reason to cut back on the aggression... It's just something you should look at as you go... Everyone focuses on how they can win more, but a really good player also spends a lot of time analyzing how they can lose less.
Depending on the size of the pot, the bet I am facing, and position, I am going to generally see a flop with any pocket pair... Yes, even Ducks. There was a time when I'd auto-fold wired 2's to a $1 preflop bet at a $.10 / $.25 table. Now I'll generally call that bet, even when it'll put me HU with the raiser. I'll almost certainly call it from position. If a 2 flops, it's time to look at the board, consider the hands and draws I might be against, and plan my next action. If it doesn't, I'm either going to consider the hand folded weigh my options on making a move, remembering that 22 still beats AK on a flop of 469. Generally, though, if I miss the set, it's easy enough to get out of this situation without losing much, if any, more than the initial call.
Remember you'll flop the set about 1 in 8 times. So what you should do, based on your past experience and the current table, is estimate the average value of the hand if you do flop the set. If they're not paying off a lot, maybe you lay it down anyway. But, generally a $.10/$.25 is very profitable on a fairly typical flop of K29. He's going to overplay top pair, as almost all of these players do, and you're likely to make a nice profit... Probably much more than the $8 pot required to make the call. (Speaking for myself personally, I probably average more like $15 - $20 pots when I flop a set. This scenario has definitely proven my most profitable area so far.)
Next time you look down at that tiny (or midlin) pair and think "it's only a pair of 3s (or whatever)", consider the potential of the hand before laying it down. You may be folding a goldmine to a relatively small bet...