Teamwork is key, and taking it slow and methodical.
Flying low or high depends on the defenses and your play style (it's a game after all, the key is to have fun).
However being too high up is detrimental, it'll be harder to see things out of the cockpit, since the ka-50s built like a tank, and the shkval doesn't work so well when you look down, since the zoom is quite high, as well as when you get shot at by something there will be no cover anywhere.
You can look at it like this, to play successfully, think of how the infantry would move always, moving from cover to cover, and always scouting out the location where they are going to move to, using bounding, yada yada.