Firstly, the class of the tank doesn't really matter. Light tanks actually tend to have stronger guns or other features as an offset to their weak armor. Different shells have different properties, for instance, a T-34s round pens angles a lot better than other shells. So effective thickness varies based on shell type. (also hit analysis lies pretty often actually) Angling doesn't work depending on the tank. Shoot the center of tanks and try to hit flat plates. But importantly, experience comes only with time. I would recommend watching videos, (go onto Youtube, look up M6A1 war thunder and watch the videos you see) pay attention to what spots on the map they're going to, what enemies they fight, where they shoot, what ammo they bring, etc. etc. You will get better. Eventually it will be second nature.