There is two ways that I know of:

1. You get lowering blocks. They are small rectangluar tubes of steel that are placed in between the axle and the leaf (where the U clamps are situated). Due to the leaf spring going under the axle, this pushes them further down and lowers the rear.

2. You have one of the leafs inverted. When the leaf is turned upside down and uses the same mounting eyelets, it pushes all of the remaining leaves down a little flatter.

Someone else can probably explain that a whole lot better for you.......

I have 2 utes, 1 method on each. i will take some photos tonight and post them up here.