Battlefield Heroes is a solo friendly game. At the same time, it is a team-based game. There is no free-for-all or deathmatch game modes. Each round focuses on team vs team capture-the-points gameplay. So, while a good solo player can do well, a few team players can dominate. The key to this domination is making sure to share all of the Heroes different group abilities.
Soldiers are the pen-ultimate team player in BF:H. They provide the healing! A Soldiers healing ability is great by itself, but when it hits multiple injured team mates, the healing is increased and the points gained for healing are increased. This is a great incentive for EVERY soldier to be a team player. Soldiers are the cornerstone of BF:H grouping.
If Soldiers are the cornerstone, Gunners are the brick walls, roof, and bell tower. With the recent Heroes of the Fall update, Gunners received a couple boosts to their team play. First, their shield ability is now shareable for those around the Gunner. Never charge into an enemy hornet nest without a shield up and running.
Secondly, a Gunners explosive keg now has a slow-down attached to any enemy it hits. Since commandos and enemy Gunners are always trying to sprint away, slowing them with a keg is invaluable when trying to lock down an area.
Also of importance is the Gunner's Leg It ability. Once used, the gunner and everyone around him will gain a boost of speed. Since vehicles are first come, first serve, a team will always need a speed boost to get where they are going. Once in combat, speed kills and makes for frustratingly hard targets to hit.
Lastly, Gunners are the best tank killers. I recommend that any Gunner spends a few dollars and buy a permanent rocket launcher in the BF:H store. Yes, spend money on a free game! Save those VP for band aids!
Out of all the classes, the Commando is by far the weakest team player. They are stealthy assassins, not hard charging knuckle-draggers! However, there are some abilities they can use to assist the team.
First off, mark target is invaluable for outing hard to find enemy commandos. Once lite up, the team can easily take care of the rest. At the minimum, it will make most enemy Commandos retreat while the mark wears off. A marked and dead Commando is better, but a retreating one isn't too bad either.
Secondly, with improvements to troop trap recently, Commandos can be very useful while staying completely stealthed. A good commando can skirt the outside of a battle and drop troop traps behind enemy players. Then team mates can try and force the enemy towards the troop trap. All of this, without the commando having to unstealth.
Don't forget, commandos are great at sneaking up on tanks and planting TNT! Combine this with a Gunners rockets and tanks are nothing more than easy kills.
Remember, sharing is caring!