The amount of charcoal you use depends on what you'll be smoking. If smoking smaller size foods, or quick cooking foods like fish, chicken parts, etc., start out using 1/3 to 1/2 pan full of charcoal briquettes.
If you are smoking a whole brisket or a pork picnic shoulder, fill the pan up completely with charcoal, because it will be cooking for a long, long time.
To extend the burn, you can fill the pan up half full with unlit charcoal, then top it off the rest of the way with hot coals, lit in a charcoal chimney.
Using this method you can place wood chunks or chips under the hot coals to provide smoke. You can add handfuls of soaked wood chips or chunks on top of the coals too, however they might flare up, raising the smoker temperature. To prevent that, wrap the wood in foil before placing on the hot briquettes.
