Welcome to the Dutch Oven Corner, where we’ll give tips and recipes for camp cooking using Dutch Ovens. I am not an expert and that you don't have to do things the same way I do.
I am always having people ask me, "How do I know how many briquettes to use?" Here is a formula that I find works really well as a starting point. Keep in mind this is just a basis to start with; you will find that you may want to alter it to fit your needs. You will also have to alter it to compensate for windy or cold conditions.
I use a basic four-and-four method. You simply subtract four from the diameter of the oven and put that many briquettes on the bottom. Then you add four to the diameter and put that many on top. Example for a 12 inch oven: 12 - 4 = 8 bottom briquettes. 12 + 4 = 16 for the top. That gives a medium head. You adjust up or down to make the oven hotter or cooler.