Ok start with this...
[youtube]/-210MIz8g80[/youtube]
I've also used the +3/-3 method.
http://dutchovendoctor.com/temperature_control.htm
Every oven is slightly different and has it's own quirks.....just like a home oven...but once you get use to it it's as easy as pie... :haha:
For hardwood fire coals from the fire, I use the had test same as I would for a grill.
The Hand Test
The other way to know the heat is to extend your palm over the charcoal at a safe distance. Imagine a soda can is standing on the cooking grate, right over the coals. If your palm was resting on the top of the can, it would be 5 inches from the cooking grate. That’s where you should measure the heat of charcoal. Always pull your hand away from the heat before it hurts, and be sure that nothing flammable, such as a sleeve, is dangling from your arm. If you need to pull your hand away after 2 to 4 seconds, the heat is high. If you need to pull your hand away after 5 to 7 seconds, the heat is medium. If you need to pull your hand away after 8 to 10 seconds, the heat is low.
High (450° to 550°F): 2 to 4 seconds
Medium (350° to 450°F): 5 to 7 seconds
Low (250° to 350°F): 8 to 10 seconds
You'll notice on the pie above I lumped all the coals in the center.....I did this at the end of cooking trying add some color to the center of the pie..
If your dutch oven doesn't have a flat top for coals.....make a pan out of tin foil and place it on top of the lid....it works very well.