Roll your pastry out by pressing down on it with even pressure rather than stretching it to fit the tin, then rest it to allow the gluten to relax.
Line the pastry with baking paper and enough dried beans or rice to keep the base from puffing up as it cooks. You can prick the base but make sure you don’t prick through the pastry.
If you are adding a liquid filling, for example a lemon tart, then brush the cooked case with a lightly beaten egg white and set it in the oven for a minute. This will make it waterproof.