I've done three just following the directions whcih come with the Gates Belt/Kit. I use a mirror on a stick to make absolutely certain the three notches on the cams and crank are lined up. I'd encourge buying the Gates belt if you can as I bought a different brand which was a 1/2" or so off.

Depending on the mileage and your finances it is a good time to swap the water pump as well.