It should sit in a dark corner at the back of your closet. Heh.
In general, you shouldn't use a lifting belt. Turn your midsection into a slab of muscle so thick and strong that you don't need a lifting belt. The only time I would suggest using it is during maximum attempts; personally, I don't even belt up then. Otherwise, you should develop your core strength by not using one during compound lifts.
Honestly, I don't even know the perfect spot to wear the belt, I have never really used them. I imagine the bottom of the belt should be at your waist line so that the belt supports your lower back, but let someone with more experience support or refute this claim before you go along with my advice.