I don't play them for the reason Briacheck said ... I don't want to chase draws. Leave them to the idiots who will call pot-size bets with them and miss them most of the time.

I limp with them on the button or CO if:
- My stack is at least 40bb
- There are at least two limpers infront of me
- The 2-3 players behind me aren't extremely shortstacked or aggressive

A recent example:
Second hand in a SnG today I pick up QTs on the button, a pretty junky hand normally. I have 4 limpers infront though so I decide to limp as well.

Flop is J9x with one of my suit. So I have an open-ended straight, backdoor flush and an overcard (which may or may not be live). That means ca: 10 outs realistically. SB leads out with an 80 bet into a 120 pot, two people call so I have great pot odds for my draw and call. Turn is a brick (not my suit), SB leads out for 40 now (super weak), everyone calls including me. River is an Ace. Everyone checks to me, I bet the pot, everyone folds. Since everyone showed such weakness I reckon the chances of me being called on the end with a scare card on board is less than 10%.

But you really need good circumstances to play these weak hands.

Well the 4 criterias I mentioned (position, stacksize, limpers, players) aren't THAT exotic, but yeah, it won't happen all the time.