Here are the most useful "tips" I received and followed as I was learning DO cooking. I still use them 10 years later:
1. Use briquettes, and put 1/3 of them under the DO and 2/3 on the top. Arrange the ones on top in a ring around the outside edge.
2. 30 briquettes produces about 350 degrees.
3. Rotate your DO 90 degrees every ten minutes. After you rotate it, rotate THE LID back to its original position. (This keeps any hot spots from burning what you're cooking.)
4. Use two firebricks side-by-side to give yourself an insulated and safe 9-inch-square platform for building your fire.
5. Don't feel like every step of the recipe has to be done on the fire in order for your meal to be "authentic." A lot of times I start out with the DO on the range-top to get things started, then I move it to the fire for the 30 to 45 minutes or more needed for baking.
Mostly, have fun and don't stress out!
-Speak