Be careful not to tear the pad. Then, reheat the key applying light pressure on the key to seat the pad evenly. If a pad becomes frayed, obviously, it must be replaced. However, in an emergency situation, simply cut a piece of plastic food wrap, stretch it tightly over the pad surface and secure it with tape or a rubber band on the outside of the key. Although lacking in aesthetic appearance, often this makeshift repair will allow the pad to seal and get the player though a concert.
Pads often stick because of high humidity.
The best approach is to use cigarette paper, which is chemically treated, to remove any residues. Place the paper under the pad, depress the pad with a moderate amount of tension, and slowly draw the paper out from under the depressed pad. Repeat this process several times. If cigarette paper is unavailable, try some other coarse paper, such as a dollar bill. Be careful not to use too much tension with delicate pads, such as those on the flute, clarinet or oboe.