The three of a kind, also called set or trips, is the best combination formed by the open cards in 7 card stud, and the higher the rank the better. A set can help you win even if you don’t improve the hand till the end of the game.
If anyone suspects that you are going to have a set, he will fold right away. The usual recommendation in this case is to be very careful and try to hide your cards. Place bets sensibly, check or call when it is necessary. You will need to keep the players in the game as long as possible because you are going to win the game. This type of playing is called “slow play” and it is used in order to increase the pot.
In case you have the so called “scare cards” i.e. Aces or Kings, or the highest up card (door card) you should take into consideration that each player expects that you’ll raise and if you don’t do that, your opponents will be very worried. On the 4th street you need to continue playing slowly because you don’t need to scare off other players. But on the 5th street it is time other players to pay for staying in the game. If they are still playing, there is still a chance that they’d like to see the River (6th Street) and they won’t be scared off.