It really depends on what your grilling, Sea food requires less heat than a burgers hot dogs & chicken, Steaks & Chops need more. also the amount of food you will be cooking at once will determine how much your going to use and how you lay out the fire.
Shrimp on a stick, fillets and such cook fairly quick and need less heat, if your cooking for 2, 2 hand fulls is sufficient, if you cooking for a group about 1/3 of a chimney
Burgers,Dogs, Chicken, 1/3 of a chimney for a small cook 2/3 for a large cook
Steaks & Chops small cook 1/2 chimney, Large cook full chimney
Charcoal Briquette Heat>> 24 briquettes arranged in a 12 " circle will give you about 350deg each one added to that amount will increase the temp about 12 deg running with the intake full open. The more you spread them out the lower the overall heat will be, To maintain 350 you need twice as many coals in a single layer as the area covered in inches of cooking surface.
I never met a Cow that I didn't like with a little Salt & Pepper! Certified PORK-A-HOLIC