For most of us this is an athletic and leisure time endeavor. I take off my engineering hat at approximately 5:00 pm every weeknight.
But seriously, I think the simplest way to do it without the benefit of any sophisticated meters (that most of us don't have and simply aren't going to waste money on) would involve the classic coast down test (recording terminal velocity) on a known (constant) gradient. If you have a steady grade that is long enough, and bearing drag can be assumed to be negligable for the sakes of the computation, then what would be better?