Best thing you can do, especially starting out, is to keep a log of your smokes. You have to have a base to start with and make adjustments as you go.
Dump your charcoal in, lit it and regulate your smoker so you maintain a desirable temp, say 230 degrees. When your temps start to go down, add more, but make a note of how much you added. Is it cold out, warm out, windy, rainy, those things come into play and with a few smokes under your belt, you will have a better understanding of how your smoker works and reacts. Its different for everyone and you really have to just get in there and do it. After 3 or 4 smokes, you will start to get the hang of it and it will become easier, guaranteed.