There's nothing more frustrating than a pair of glasses that just doesn't fit right. Minor repairs and adjustments are almost always free at the shop where you purchased the glasses. If it isn't possible to take them back to the shop, there are short-term remedies you can use to make your glasses fit better.
Know the parts of your glasses. The temple or "arm" holds the glasses against your head, the nose pads rest on the nose, and the earpiece curves around the ears to help hold the glasses in place.
Consider the type of frame you have. Metal frames are much easier to adjust. If you have plastic frames, take the glasses to a pro as they will need to be heated to alter.
Determine the problem. If glasses sit too high or too low on your face, or if they are sitting too far to one side or the other, the problem may be with the nose pads. If glasses sit cockeyed, the problem is probably the arm or temple. If the arm digs into your head at the end or sticks out too far, the problem is the earpiece.
Fix a nose pad problem. If the glasses sit too low on your nose, gently twist the nose pads between your thumb and forefinger, pressing in at the top and bottom. If they sit too high, slowly twist the pads out. The nose pads should fit flush against the nose, without leaving pressure marks on your skin.
Fix the temple or arm. If the glasses are off balance, place them on a hard surface to determine which side is off-kilter. Use needle-nose pliers to gently bend the frame until the two sides are evenly balanced. Use caution to avoid snapping the weld point. If the glasses are squeezing the side of your head, carefully bow the arm or temple out away from the head. This will reduce the discomfort. If the temples push too much on the head, they can also cause the glasses to slip forward. Bend the temple out slowly with your hands.
Adjust the earpiece. If the earpiece at the end of the glasses is poking into your head, gently bend it into a better position. If the earpiece is digging into the back of your ear, press the middle of the earpiece with gentle force until it fits comfortably.
Carefully polish your glasses with a soft, nonabrasive cloth. This will remove any fingerprints that may have got on the lenses during the adjusting.
Be patient. Rushing through a fix is a sure-fire way to make the problem worse.
If you feel that you are forcing the frames at any point, stop adjusting. You may risk breaking your glasses.