Also if you over mix the dough. My grandmothers used shortening (Crisco) in their biscuits, and White Lily flour (it's a southern thing). It seems that the buttermilk recipies (or use sour milk) makes a bit "lighter" biscuit too.

And if you want to be decadent, melt some bacon drippings in the pan (put in the oven while it's pre-heating). After you've cut your biscuits out, coat both sides in the melted drippings, then bake. (It helps if you slant the pan, so that all the drippings are at one end.)