Always have someone staying back behind the enemy's line of sight.
Have each of your teammates be one weapons class.
Assault - Best is the AN-94 Abakan with 4x scope and Magnum ammo.
Engineer - Always have the M2 Carl Gustav AT with Extra Explosives
Medic - Lay down fire and stay a bit farther back, healing and reviving your teammates when needed. Always have a tracer dart as a medic, you have enough bullets to load out regardless.
Recon - Always have mortars and keep the enemy at bay and not to advance to far on you.
First Flag - This one shouldn't be to much of a problem until the chopper comes. Be ready to have the tracer dart with your team and once it is traced, eliminate it with a Rocket as fast as possible. The faster you destroy this chopper the easier this flag will be to over take.
Second Flag - The second flag has many Heavy MG's located around it. Have 2 Engineers move up as some of the enemies are killed and use the Rocket Launchers to take out the Heavy MG's with ease.
Third Flag - This one may prove to be the toughest. A tank appears and can be tough on your team if not taken out quickly. Have a Recon call in a mortar strike or 2 engineers shooting Carl Gustav's with increased explosive damage. Once you have cleared the enemies front line, they spawn in the far right and left corners of the map. Have a medic go up to the flag and hide behind the crates. Everyone else set up camp and protect your medic from different angles(Recon snipe from a distance and 2 Assault classes kill any enemies they see advancing on your Medic.