Learn What Ammo to Use
Did you know that there’s more shell types than just APCR? There are more than half a dozen different shell types in World of Tanks, each offering a specific advantage over the others. Using HE rounds in one situation might net you better results than using AP or APCR.
AP are your standard Armor Piercing rounds that each tank comes equipped with (unless you’re using an SPG, Howitzer, etc). These rounds will typically get you through many engagements, but sometimes you might encounter a situation where they’re useless.
When facing a Heavy Tank you cannot damage, you could try moving around it and attacking its sides or rear, or you could try HE rounds. HE rounds depend on impact damage as opposed to penetration, and will typically always deal some amount of damage.
Then there are rounds such as HEAT and HESH. Even the mighty Maus will be destroyed by the HESH rounds fired by the FV215b (183). HESH rounds are also useful if you want to specifically target the crew of an enemy vehicle.