You should have a read of G W Sears' (Nessmuk) Woodcraft and Camping, great book with a nice chapter on camp cookery. Plus its a free download in the articles section
Unless you're "smoking" then neither of these. You need coals (preferably glowing for the highest heat) Probably what Ogri eans when he says "embers." That's where the real heat is. Also the consistent heat.
Here's a few videos demonstrating the technigue (granted he's cooking at a fireplace in a cabin but the technique is the same):
www.youtube.com/watch?v=xTqI0b1xwCs and www.youtube.com/watch?v=mysiBE3qX1k and www.youtube.com/watch?v=uvjVZSmFmg8
These not only show the technique but give some good recipes as well.
You should have a read of G W Sears' (Nessmuk) Woodcraft and Camping, great book with a nice chapter on camp cookery. Plus its a free download in the articles section