Tips for becoming the king of the tanks:
1: Awareness is everything, learn what colour tanks do which attacks, and always remember that you shoot faster than they do, so if you face a tank head on and shoot continuously their shots cant hit you (works especially well with the missile guys).
2: Beat bouncing missile guys at their own game, and make full use of bouncing bullets. Im not saying use a pretractor, but experiment with using angles to hit round corners, minimising danger to yourself. Always remember that they can bounce too, and remember which lines they can shoot along.
3: Use your environment, staying stationary in the open is asking for trouble, as most tanks fire at your current position, by simply moving side to side behind a wall you can avoid 90%+ of attacks.
4: Spray 'em, when hiding behind a wall, pop out and shoot 4 shots, but not in the same line, try and scatter them a little, that way you can get bounce kills and kill them even if they dodge one. Its always handy to save that 5th bullet in case you need it in an emergency!
5: Practise, at the end of the day this is what it comes down to, that is how ive worked out these tips, and im sure some people have different styles and would do things differently, but as soon as you get into the zone its a good feeling!