Taking good care of your eye glasses:
Don't wear your glasses on the top of your head! The crown of your head is wider than your temples and your frames were designed to sit on the bridge of your nose. Wearing your glasses like a headband will strech them out and damage the frames.
Put your glasses in their case when your not wearing them. This protects them from heat as well as random accidents that might scratch the lenses. Try not to leave your glasses in direct sunlight or a hot car. Extreme heat will damage the frames.
Periodically check your glasses for loose screws and tighten them before they fall out. You can get an eyeglass repair kit with the right size screw driver at just about any drug store for a couple of dollars. If you bought your frames at Costco, they will adjust them for you anytime for free.
Keep your glasses clean by using a soft microfiber or cotton cloth. Do not use tissues or paper towels because the fibers will scratch the lenses. Costco optical sells a nice lens cleaning kit that includes a spray bottle of cleaning solution and a special microfiber cloth. There are free refills on the solution, you just bring your empty spray bottle in and help yourself at the dispenser on the counter.
Lotions, make up, hairspray and sweat can damage the coating on your lenses. Clean your glasses right away if they come in contact with any of these things. You can use a little bit of gentle dish washing soap, like Ivory or Dawn, and some warm water if you don't have lens cleaner. Use your microfiber or soft cotton cloth to dry them off.