There are four squads in a MAG platoon - Alpha, Beta, Charlie, and Delta. Membership of a specific Squad dictates which part of the map you will appear in (unless you choose to alter the Spawn Point).
At full strength, a Squad is comprised of seven Troopers and a Squad Leader. The effective trooper strength may be slightly lowered by the inclusion of a Platoon Leader or Officer in Charge, but the special area-effect abilities associated with those positions usually more than compensates.
In combat, a well-trained Squad versed in combat tactics and under the command of a good leader can smash through far larger forces, assuming that the larger forces lack the communication ability and/or competent leadership.
Squads can be reduced through players resigning or getting Kicked. Should a player leave the Squad during the operation, He/she will not get any of the points earned up to that point.
A balance of normal Troopers compared to Commandoes and Snipers is essential to a good squad. For instance, more than 2 snipers to a squad can lower it's effectivness, but no snipers can leave them without long-range support, and thusly an effective way to deal with enemy marksman. Well-trained Squads often utilise the Fireteam technique, splitting into two smaller units for advanced maneuvers.
Another good tactic is to make sure that at least one of the squad has a Medical Kit and proper perk training, lest you all fall down without an arm to pull you back up. Keep in mind that a Medical Kit often comes with a Field Support player, who may not be as effective in a firefight, but should keep you all in good health or from dying absolutely.