Unlock Levels
You can unlock the foundation MP map by finishing campaign mode on easy. there are also two other maps to unlock: Marathon and Conclusion. Try finishing harder campaign modes to unlock these levels.
Multiplayer Map - Foundation
Beat the single-player campaign on any difficulty.
Tactics
If you are in a closed area (small room, hall way, etc.) then hold only 1 weapon, so you can throw grenades. If you are in a open area (big room, outside, forest, etc.) than have 2 weapons in hand because grenades will be useless.
Be The Gunner
Get to a 'Hog and jump in the gunner/passenger seat and let the marines drive. It will be x2 more effective than you driving (it depends on your skill).
Weapons List
Here is a Complete list of the weapons:
Legend:
x:can dual
h:can head shot
z:can zoom once
z:can zoom twice
l:can lock on
s:Splash damage
b:uses a battery(non reloadable)
sp: Single player only
Weapons
1.Magnum(pistol) x,h
2.SMG x
3.Battle Rifle z
4.Shotgun s
5.Sniper Rifle 2z,h
6.Rocket Launcher l,s
7.Plasma pistol x,b
8.Plasma rifle x,b
9.Brute plasma rifle sp,x,b
10.Covenent Carbine 2z
11.Brute shot s
12.Needler x,l
13.Covenent sniper rifle 2z,h,b
14.Fuel rod cannon s,sp
15.Sword l
