I run the media tech department of a university, so I have more experience than I wanted to ever have with how to treat cables right. Put the spring of an old ball point pen over the end of the cable right where it comes out of the magsafe block. Never wind the cable tightly around other things (e.g. the charger block), cables typically have a minimum bending radius that you should not go below.

Do this and the cable will last longer than the computer (freak accidents excluded).