Earning experience is vital to advancing in the game, and can be earned in a number of different ways:
1) By “spotting” an enemy vehicle for your allies, if it is visible and within your view range.
(You will get more experience for discovering an SPG than for a regular tank.)
2) By dealing damage, critical or otherwise to enemy tanks. (The difference in amounts of damage is a factor.)
3) For damage your allies cause against a vehicle you have spotted.
4) By capturing the enemy base.
(This applies only to the tanks in the enemy base circle, not the whole team, and is proportional to the time spent in the enemy base circle capturing it.)
5) Restarting the capture counter by damaging an enemy tank which is capturing your base.
6) Bonus experience for staying alive is also obtainable.
7) “Active military actions” are also factored in. This includes splash damage from high explosive ammunition
8) The winning team will receive +50% bonus experience which stacks with the score of each tank individually.
You will not receive experience for:
1) Damaging or killing an ally's vehicle. You will in fact have proportional credits and XP deducted, and may face a game restriction.
2) Ricochets or "non-penetrating hits."
3) For receiving "Battle Hero" titles in the "After-Action Report" window (Except for “Invader” and “Defender”).
4) Fighting in a draw or lost battle will lead to XP without the 50% bonus.*
An alternative for elite or premium tanks is to check the “accelerate crew training” checkbox above the crew which means that your crew will be trained faster at the expense of convertible experience.