Here is a full tutorial on making Charcoal and Biochar using the Brick Chimney Kiln.

The topics covered in this video:
How to build the chimney and materials needed
How to use the chimney
Wood stock and cans
Firebricks vs. Clay bricks
Different results

Here are the recommended tutorials mentioned in the introduction:
* Peter Hurst New England Biochar; he does a good job at showing how a retort system works
   • MAKING BIOCHAR: with Peter Hirst of N...  

* John Rogers Biochar for the small farm; he has access to lots of woodchips, and has a burn method showing the process.
   • Making Biochar For Small Farms  

* Kelpie Wilson Flame Cap Kilns showing three different methods of an open burn
   • First firing Ring of Fire Kiln