Haven't had the chance to cook on it since my brisket cook a while ago, but when I use it, coals just go in the middle. Read a heap of different ideas about where to have the fire and just settled on the middle. Some say near the air inlet, others say nearer to the cooking chamber, others in the middle. So middle is where I sort of start out.
From my experience on Barry I found building the heat source furthest away from the entry into the main chamber worked best.
I found the trick was to build a small enough fire with the vent on the fire box always fully open.
this promoted a clean hot fire with blue smoke when using wood chunks.
Found i got the best results doing this.
The other thing I found was putting in one of those half grates from the fire box in closest to the entry to the main chamber and putting in a water pan so the temp didn't fluctuate as much.
All my trade secrets for Barry are out now!!!