Well, one top tip would be to join in with the OcUK squadron, and we shall teach you the ways of the War Thunder low-level tankings!
Apart from that, for the moment one of the best bits of advice I can give is to learn how the Battle Rating (BR) system works, to determine what size/type of enemies you'll face. At the moment if you're still playing reserve (BR 1.0) tanks it won't matter too much, and if you stick with the Americans and unlock a few tanks before you get the M3 Lee.
The matchmaking in Tanks works by putting you into matches of the difficulty of your highest BR'd tank - so for example if you play Germans, and unlock the Stug first and put that in your lineup, you'll have a BR of 2.3 which means you'll be facing up to 3.3BR tanks, and you'll have one tank that can dent them, and 2 others that can chip their paintwork
So in short, keep the BR lineups as level as possible - step up from reserves to 1.3's, then 2.0's, then 2.3's, then 3.0's - even if you have to not drive a tank for a bit until you have something suitable to equal it. You'll find sweet spots for various things when you figure it out.
Actual tanking tactics though?
Shoot them in the sides, rear and turrets.
Don't fill your ammo loadout full, and don't bother bringing HE shells they're useless (the less shells you have, the less chance of an enemy shell hitting them)
Don't be a rambo and try and take on their team solo, you'll just die
Work with other tanks to use their strengths to your advantage - to learn what tanks have slow rates of fire, and cover their flanks.
And learn to capture the damn map points.... we get so many rage moments where we lose battles because idiots won't drive 6ft forward into a capture circle
Anyway, thats more than enough theory to start off with - just get out there and murder them for now!