Form a Solid Team
Once you're in a Squad you'll want to make proper use of it.
For one, you'll want to diversify your classes. If you choose classes that compliment each other (for instance, it's probably not a good idea to have five Scouts in your squad) you'll have a much better chance against your opponent. Remember killing people and taking objectives is the name of the game here.
If you're a Medic you'll want to throw out health to your squadmates and anyone else looking for health. If you're playing a Support class, throw out ammo when you can. You'll get some easy points if you do.
If your squad works well as a unit you'll receive XP bonus multipliers when you take certain actions. These multipliers are essential if you're looking to move up the ranks quickly.
Also remember that dead squad members can spawn on members who are still alive. If you die, don't waste your time running back into battle. Carefully select a a squad member to spawn on and jump right back into the battle.
If you're the last one alive, find a place to hide and you'll get a nice bonus when a squad member spawns on you.
The Squad leader is also able to issue orders. If you're the Squad leader you'll want to issue waypoints on the map.
If you're a Squad member, you'll want to follow the orders (assuming the orders make sense). Following orders will net you extra experience.