Avoid screwing your eyes up, tight blinking and as mentioned above, squinting. A good eye cream for the day is essential (Espa has a great one) and Vitamin E oil applied around the eye area (carefully) at night also helps.
Take your eye make-up off with baby oil at night. When you wash your face afterwards with warm water, the oil disperses but protects the skin
I have been doing this for years and I hardly have any crows feet - unlike my younger brothers!
When cleansing your face in the eye area, start at the bridge of the nose below the eyebrow, clean in a straight line along below the eyebrow to the outer corner of the eye, then continue below the eye back to the bridge of the nose completing the circle. This is a very sensitive area so be very gentle so as not to damage the skin.