Temperature control does not come naturally. It has to be learned and takes several cooks to get comfortable. There are many variables that play a role and my suggestion is to keep as many variables the same for each cook until you get comfortable. Use the same types of charcoal, use water in the pan every cook, use the same thermometer/temp probes, etc. Once you get comfortable you can start experimenting with different types/brands of charcoal, cooking with a dry pan or sand in the pan, etc. The biggest problem for new cooks is realizing that temps react slowly to changes. You need to make changes WAY BEFORE they are necessary. If you are shooting for 225* and using the minion method then you'll start with a handful of lit coals (depending on outside temps). I usually open my vents all of the way to get the fire burning. As I approach 200* I start closing down my vents so all three are cracked open. I can then judge (this is where experience counts) how much to open each vent to reach my goal temp.
As complicated as it may sound, it really is simple. It just takes time to learn. Keep cooking every weekend and you'll be an old pro before the summer! Good luck and happy smoking.
Russ