[Pov]

Your ideal pot is unraised and 5-handed (or more) much like it is with a small pair. You would also prefer a table where there is not a lot of raising on the flop so you can see a cheap 4th card or make a free card play with little risk of being 3-bet when you flop a good draw. (The pair actually likes a lot of raising on the flop since you'll have either hit your set or have missed it and wouldn't be calling a single bet most of the time anyway.)

So assuming you are in late position you would like to see 3 people limp in front of you. You can get away with just 2 limpers if the small blind is likely to complete or there is a loose button, etc. Just be aware that playing these hands against too few limpers is trouble.

However, if 3 players limped then someone raised in a lot of the low limit games I play in I would probably cold-call with T9s or 66 since it is now likely that this will be a large multi-way pot. The limpers will certainly call and the BB and probably somebody else will too and I have good position with a hand I can release if it doesn't hit hard. This is one of those high variance plays (i.e. not for small bankrolls) since it tends to miss frequently but wins a quite large pot when it does.