1) Learn about phase and using more than one mic.
2) Put it where it sounds good for what you are doing, plain and simple. Up very close, on the grill, will eliminate more room noise and ambiance if its a crappy sounding room, but wont sound as natural as having one about 6 inches or more back. The tradeoffs can be severe in a crappy room. I have some 3 inch thick foam like mics are packed in, some big squares, and I put the mic about 8 inches back, between center and edge of cone, and build a tunnel around it so that I dont get any room sound. Put a chair in front of it and cover it with about 3 packing blankets where sound has trouble getting in and out and it'll help a lot too.
3) experiment with two mics at exactly the same distance from the cone, and experimetn with one close and one a foot or two back, and beware of phase problems.