How do you guys keep track of all the different tanks you face?
I met an AT 2 for the first time yesterday. He was slugging it out with a heavy. I was in my M2 Med with derp. I said OK, Tier V TD, strong frontal armor, but vulnerable from its flanks. I'll use my speed and get around it. Get to the side and aim for the rear hull, derp...no damage. Ok, strong side armor too, he's still distracted i'll get behind him and derp him good. Get right behind him and aim for the flat part of hull between the tracks. Derp!...no damage, uhh, lower part of the hull? Derp...no damage. turret area? please? Derp...14 damage. Ahh fudge, by that time someone one shot me. I didn't even knock out a freaking module.
I'm slowly learning who to go against and who to run away from, but geez there are a lot of tanks to remember.
For a lot of tanks, especially at lower tiers, shoot for "obvious" weakspots in armor: commander's cupolas, machinegun ports, hatches, etc. That will help a lot.