If a few people limp in and you are in the small blind with a junky hand, you should usually fold instead of putting in the extra ½ of a big blind. While it may be tempting to call due to your amazing pot odds, with junky hands like 94o and 73o, you will not flop well enough to justify calling.
You will find that what often happens is you either totally miss the flop or you flop a marginal one pair hand and end up losing some additional amount of money. Even if you happen to make a strong hand, such as bottom two pair, if someone wants to put their stack in, you are usually beat.
I take this a step further and fold any hand I expect to be dominated. For example, if four players limp, I will fold K6o from the small blind. However, if only one player limps, I am much more inclined to call or raise because I will not be dominated nearly as often and a flopped one-pair may be good enough to win. In general, as more players limp into the pot, hands with one big card and one little card drastically decrease in value because they are much more likely to be dominated. The last thing you want to do is play a pot out of position with an easily-dominated hand.
If you decide to see a flop from the small blind in a limped pot, you must play well after the flop. For example, if you call with J7o from the small blind and the flop comes J-8-4, there will be times when you should lead into your opponents, check-raise, check-call, or even check-fold. To make your decision even trickier, there will be times when you should drastically alter your play based on your opponents’ tendencies. If a loose, aggressive player bets and a loose, passive player calls, you should usually check-call or check-raise. If a tight player bets and a tight player calls, you should usually check-fold. If you decide to play with junk, you must play it extremely well if you want to profit.