The main factor dictating water change schedules is whether the tank is cycled or not. If it's cycled 25% water changes weekly or biweekly should be sufficient. Never do 100% W/Cs on a cycled tank because you will remove the nitrifying bacteria.
If the tank is uncycled, anthing other than a 100% water change is pretty much useless so you will want to clean the whole tank out twice a week.
Yeah if you don't cycle it your going to have to do 100% water changes once a week. If you want to cycle than a 25% change would be fine. Cycling a tank that little would be really fast... just look up how to do a fishless cycle or a fish in cycle (depending on which one suits you best).
@reaperss06.... I would think so. For me anything under 5 gallons would get 2 100% changes a week (if it were uncycled)... averaging to a wc about every 5 days. Anything under 2 gallons would get a full water change every other day or everyday if it is a hospital tank.
But from what I've read it really depends on the tank. I've heard some people testing their water daily and only doing 1 full change a week on 2 and even 1 gallon bowls. For me I always go for more water changes... a better safe then sorry approach.