Also as my personal set of advices.
~ Bring long spear, bamboo spear , any support weapon realy if you can, have you ever seen 7 bamboo spears in one team working together.~ITS AWFULL
~ Know each map , and always try to see the battle from the overal vieuw , what i mean that if 75% of your team goes left and then at the left side of the map you only notice very little enemys you know that there team went right. Sounds stupid but most people seems to fail at that , also know that those small group of enemys you encountered are fucked because you outnumber them big time.
~ Listen to good rock music while fighting : guns n roses , nickelback etc !! very important.
~ As for siege FOR THE LOVE OF CHRIST let the fuckin shielders go up the ladders first.
~ As in battle keep an general idea of where your enemy is , and how your team is doing and ESPECCIALY where you're needed.
~Also as corwin stated your battle awereness is important , dont get cav fucked , dont get archer fucked , dont get ganked. A good way to prevent most of this is to stick to the big group of your team and know the position of your enemys aswel.
~ Know yourself , what i mean with that is that if you are an agi build you dont want to be charging in the beggining of the build and risk taking that hit or archer shot. Also if your health is low at the end of the round try to play saver and stick with your team as an agi build. If on higher health you can go solo saver knowing that you can take a hit if needed or an arrow and walk. For strenght builds if the round is coming to an end and you're still on high health try to fight very agresive most of your enemys will have low health and be terrified of you being so agresive.
~ Know your weapon , if the melee battle is clashing and you got an opponent to pick , pick the one that is easily taken out by you so if you are using the maul aim for a piker/hoplite/one hander and leave the katanas en other fast weapons for the teammates at first instance. Then once the battle begins more skirmishy as an agi build try to do like one hit on one enemy then switch your oppenent to someone your aly is fighting or who is reloading or just busy in general.
~ Tell general easy commands , as in cav left , group of pikers at the right and vice versa.