make sure your team is "focusing" fire.
don't let players bring just anything make sure they have the right tank.
you don't need more than 1 scout.
it is not recommended to use heavy tanks in T-6 strongholds.
Always keep your base being capped in mind if you are getting farther away and not all of the enemy is exposed.
get to know the maps on a personal level so you have an idea of what will work.
remember there will be times when you need to have the awareness to call an "audible".
don't bring arty things happen way to fast for arty to even contribute @ tier 6.
don't split up your force, try to keep it to 1 scout checking your flank and everyone else wolf packing.
most important you will not get better if you quit. don't give up.