How much charcoal to use is an open ended question that comes down to the quality of the charocal, what you're cooking and the grill size. But, a general guideline is 30-50 briquets, or one charcoal chimney full. Remember, it's easy to add more charcoal if needed rather than trying to cool down a fire that's too hot. Start with less and add more as necessary to keep an even heat.