While practice is required to master 7 Card Stud here are a few tips to help you get started:

Push High-Pair's early.
If you are lucky enough to be dealt a high valued pair as part of your initial three cards you have a good starting hand, but high valued pairs frequently don't improve or even hold their higher value once other players are dealt more cards. So unless some other player is indicating a strong hand, you should bet aggressively while you have the best hand to try to get players to fold early rather than trying to slow play.

Consider Slow Playing Three of a Kind.
Because in 7 Card Stud two pair is often the final hand in a game it's often a solid strategy to slow-play three of a kind, especially if your opponents have a tendency to fold early, as there is a very good chance that you can win the pot. Just be careful that your opponents don't manage to acquire a straight or flush.

Watch other players' hands carefully.
All of the cards you can see on the table have to be eliminated from being available to you to improve your hand. As an example, supposing your hand is in need of a 9 to make a straight and you see three of them face-up on the table, you know that the chance of you getting the other 9 is very low. Similarly if you had a hand that was in need of one diamond to obtain a flush but eight other diamonds are showing on the table you know that at best there is only one more available and there's little chance of success.

You can also use the cards you can see to help you predict the odds of you getting the specific card or suit needed. As an example, if you have a hand consisting of four hearts and you notice that there are very few hearts showing on the table, you can use this observation to act knowing that you have an increased chance of catching the heart and making the flush.

Pay attention to the cards that are folded.
In the game of 7 Card Stud Poker whenever any player folds their cards are turned over (placed face down). Because you are now unable to see these cards it's important that you have made a mental note of what the cards were that have been folded, as well as paying attention to the remaining face-up cards, so that you maintain a feeling for the cards that remain in the deck.

Watch players' bets early to get an indication of what their down cards may be.
Players who bet early are usually signaling that they have a strong initial hand like a high pair or perhaps three suited cards. If you are able to read this player to get a feel for what their hole cards are, you can then act based on the relative strength of the two hands (his/hers and yours).

7 Card Stud has a larger number of face-up cards than in hold'em games and this enables players to get a much better feel for the cards that remain in the deck to be dealt. A player can improve their game by paying close attention to the cards that have been dealt and then acting using this additional information.