As far as fuel consumption goes, start small and keep it that way. My firebox inside dimensions are 16 x 24. Basically what I use is the middle eight inches leaving lots of room. When I bring it up to temp I start it with a half chimney of charcoal and 1 or maybe 2 splits. Then every 15 add another split or half chimney alternating. When it is up to temp and cooking I add fuel, 1/3 chimney or a couple of splits every half hour. I prefer to run it a little lean and save on the fuel, but you have to stay on top of it!
Keeping your fire lean will also help keep the bitter taste out of your food. On another thread KAM pointed out that bitter taste is cyanide from the creosote of struggling fire. Give the fire enough fuel to keep it going, but not enough that it smothers it. Make sense?