Easy experience hint:
Go to "Main Menu" > "Play Online" > "Deathmatch". Choose any map and search for games until you find one in progress showing only a couple players. The rest of the players will be made up of bots, which are easy to kill allowing you to earn killing streaks, head shots, etc., and in turn more money and experience.
Specialist - Reach Level 7.
Sergeant Major of the Army - Reach Level 40.
Master of Mass Destruction - Win one match of each game type in every map.
Raining Shrapnel - Kill 4 enemies with a frag grenade thrown with the grenade launcher.
Billy the Kid - Make 100 head shots (any game type).
Alexander the Great - Capture a total of 100 territories in Domination.
Welcome to the Family - Win a match (any game types).
The Ghost Avenger - Take over a CPU and kill your assassin 10 times (offline only).
Insane Sharpshooter - Eliminate 300 enemies only with sniper rifles (any game types).
Heavy Counter - Perform a multi-kill with a grenade 3 times (any game types).
Legendary Gunslinger - Perform at least one killing spree on all maps.
Team Savior - As the Team Leader, escape 10 times.
Ultimate Team Player - Get 500 kill assists (any game types).
Stop Poking Me! - Successfully knife 50 enemies (any game types).
War Veteran - Eliminate 100 enemies (any game types).
Death Bringer - Eliminate 1000 enemies (any game types).
Dominating - Capture a total of 150 territories in Domination.
Priceless - Head shot an objective carrier 10 times.
Hope Buster - Defuse a bomb or deactivate a missile 10 times.
Supreme Commander - Reach Level 72.