Here are some ways

Eat lots of fruits & veggies! Carrots, loaded with beta carotene are especially helpful in maintaining healthy eyes.
Avoid wearing contact lenses for more than 12 hours. This can cause permanent sight damage as well as extreme discomfort.
Use sparingly.
Using an allergen-reducing eye drop during allergy season to 'get the red out' and sooth itchiness may help on a limited basis, but chronic daily use can actually make the problem worse.
Read the labels of eye drops carefully; many drops cannot be used while wearing contacts.

Press cold cucumber slices gently against eyes 10 minutes before going to sleep at night to prevent puffiness.
Wear UV protective sunglasses. Get polarized lenses, NOT just darker lenses. The lenses that only make the world darker will just make your pupils dilate and don't do a thing to stop the UV rays. Prolonged exposure to UV rays can harm your eyesight, protection in youth can help prevent loss of eyesight in later years.

Try not to spend so much time looking at your computer screen. (As a matter of fact, now would be a good time to give your eyes a break, since you're not doing anything too important.

Be sure to wear goggles or other eye protective wear when working with chemicals or any place with harmful airborne particulates.
Take lots of Vitamin A and dont look at the sun.