As mentioned before - reading your opponents hands directly is impossible, they are hidden and it's better you won't try any cheating methods to peek at them. You can get a clue on hands by reading the players that hold them. Most Seven Card Stud poker players can put out a good poker face, but it's very hard for them to control their body language.
There are many small indications that reveal people's feelings. You might notice that certain players move around in their chair before they make a bet during 3rd Street. That means that they think about how much to risk, they calculate their odds for winning, but it clearly points out that they do not have a High Pair. A High Pair Poker Strategy at Third Street isn't very complex, but players who aren't aware of it would simply raise the stakes hoping they would scoop the pot, and players that do move around in their chairs do not hold such pair.
As you can see, by reading card-players' body language you may reveal their hands, or at least get a "feel for the game" and for them as well. If you had a High Pair during 4th Street and you see no indications that any other player holds a better hand then you may move forward, without fearing that someone would reveal a nasty surprise for you in 7th street.
But reading your opponents is not just reading body signs; it's much more than that. Reading your Seven Card Stud poker opponents hands may rely on other techniques and again - your experience, your "feel of the game" or "feel of Card Stud Poker". With time you would learn to notice all of these small signs, these would tell you if the players you're up against hold a good hand or if they simply bluff their way to the pot. Learning your card stud poker opponents is a vital part of reading hands strategy.
Daniel Jenkins, Editorial Staff. 2006-01–22