So much of what has been said is just figuring out the meta of each map. They play pretty predictably 80% of the time I'd say. Helps to know the win % of a given tank too, but if you run vanilla, you don't get that information.
Just paying attention, and having a very short debrief at the end of every game that's more than "omg my team is retarded" gets you a lot of places. What did you do that worked well, what didn't. Did any enemy really do anything you should have been surprised by? Probably not, so how can you deal with it faster and better next time?
For me, my best was playing around 3k recent, I think I could have pushed to 4k if I had wanted, but I just loved being aggressive. Even hitting 2.5k is a challenge in my current situation, I maybe try to get 1 or 2 doubles a few times a month. It can be 6 months inbetween games for me. The maps aren't really changing a ton right now, but the meta, I mean it always felt stagnant, but it does change from time to time, I can tell you that. I will get punished hard for getting early shots from a specific spot, or whatever. Still, there are general placements, or rules, that allow you to do better or worse.