To improve general performance whilst increasing the team approach:
Firstly sort out your positions, who plays front who plays back etc. Then split your team into squads, left tape, centre and right tape.
Any Drill you run ensure you are part of it you are a player like the rest and they need to see that.
Make sure the players like and respect each other for the positions they play, it is no good having a player who wont provide covering fire from the back because they don't like the player in front, or a front who wont move cos he doesnt trust hias back up.
When you have done this you play the left tape against the right, in a narrow play area, this will make the front player listen to the back player who will then have to shout(use the centre players as Marshalls). Do the same with the left against the centre players,and rotate till each group has played each other, this will promote the front players confidence of doing what the back player says to do, and to do it immediately.
If there are any disputes as to if the call was right, get the players to swap positions, and then they gain a perspective of how important timing is the call needs to be on time for the move to happen at the right time.
Healthy competion between each of these groups is good, but no one is better, as without each other the team is useless.
If you can train of Supair fields, then split the team in half, in your squad pick the fastest player, give them a difficult breaking point (but not impossible) and then use all the other players to try to shoot him in from the break, don't tell the other squad otherwise they will preempt the move, let the game role out then ask the guys what impact it had for each player on both teams.
Try again with a different front player.
When you look for these moves in a tourny remember that if the front player doesn't have his heart in it, he won't get there so send someone else.
Practise snapshooting with the wrong hand against your equals eg front against fronts, backs against backs (fronts normally need to play tighter) then mix them up, then use the right hand.
A very important thing to do off the field is socialise together, it sounds strange, but the more you like someone the more likely you are to try harder for them, share info with them etc.
Hope this helps as a starting point..