Starting with Pairs in Seven-Card Stud
A starting pair will either be wired (with both cards in the hole) or split (one of the paired cards in the hole with the other up). Wired pairs are more valuable than split pairs because they are invisible to your opponents. When your pair is split, opponents assume, correctly, that you hold a pair of the exposed rank when you bet.
High pair. We're talking about QQ or hgher here in a big game, and JJ or higher in a smaller game. You most likely have the best current hand and are on a good start toward a strong two pair, trips, or better. It is important to understand how the high pair determines the rank of any two pair that you make. If you have Kd-8s-Ks-5c-4d (underscore indicates hole cards) after fifth street, for example, there is no practical difference between making two pair with your eight, your five, or your four. Since pairing any of those cards would make your high two pair, you have good prospects of doing just that. (Your chances are much worse when you hold a low pair because you would have to pair a particular high card to make a decent hand.)
Having a pocket pair in three out of seven cards is not as strong as having a pocket pair in two out of seven cards, as you do in Hold'em. This takes some value out something like a pair of aces on third street and makes it more important to force out opponents. These are heads-up hands unless they rapidly turn into trips. You want to make money with hands like this by punishing opponents who call with lesser pairs, not by inviting players with draws to chase you. Complete the bet when the action comes to you, and if someone else completes it first, go ahead and raise if your pair beats their door card (their up card on third street) and there are no higher door cards yet to act. If a player showing a higher card raises you, you must play cautiously. If you give him credit for a higher pair, your hand is dominated and you should fold.
Lower pairs. Pairs lower than JJ can still be playable if they have a high kicker to go with them. By "high" I mean higher than any other player's door card. This is important for two reasons: It gives you a draw to the highest two pair that is evident, and a player with a higher door card would stymie you even if you paired your kicker (you would have to put him on a higher two pair or an easy draw to one). The rank of the pair you start with will rarely matter because it won't win by itself. Heads-up play is best for you with a hand like this, but if you raise, you don't want any callers. It's usually better to try to stay in the hand cheaply, or fold if you can't.
You will be doing yourself a favor by folding split lower pairs with no kicker, such as 9h-5c-9d. The only time you would consider playing these hands is in a passive crowd where you are sure you will get to see fourth street for just the bring-in bet. Wired lower pairs with no kicker, such as 4h-4s-8d, can be playable because of the good implied odds: You can ambush opponents with your hidden pair if it improves. If you play a hand like this, you should usually preserve its concealed strength and keep your costs down by just limping and you should fold if there is a lot of raising.