In this game the average winning hand is a fair three of a kind, such as three eights or three tens. There are quite a few straights and flushes. The worst mistakes made by the average player are: staying on a low pair, such as fours or fives; and staying more than one round on a straight or flush possibility.
If there is another principal mistake, it probably is in playing a two-pair hand too strongly—unless you get your two pair on the first four cards, in which case the odds are only about 21/2 to 1 against filling.
The nature of the game is such that there is a lot of difference between a concealed low pair and a split low pair. (A concealed low pair is, for example, two fours down and a king up; a split low pair is a four and king down and a four up.) Of course, your chance of improving is the same in both cases, but your chance of getting a big pot is far better with the concealed pair. In seven-card stud it is quite easy to have a full house with no pairs showing, and when you have such a hand a player with a straight or flush is very likely to bet into you, raise you, and ultimately call you, and you will win a big pot. With a split pair, if you make three of a kind early you show a pair and the other players are automatically on guard. If the case card of that rank doesn't soon show, the other players must even keep in mind the danger that you have four of a kind, and while this may put you in a good bluffing position occasionally, that is far less important than the fact that it will prevent your getting any action.