1) On missions when you have to get somthing thats neutral quickly (eg. Trailer mission/Holdouts) ALWAYS equip the rocket launcher + a kevar vest, so you can quickly blow up any baddies (!) who get to the location B4 you (you can also blow up the trailer)
Fed up of using more than one grenade/rocket on the APC? Put a buggy in the way and blow that up!!
KADABOOMMMM, APC with one grenade/rocket.
Playing holdout in team game? Why not drop your kit so another user can use it? Press Q, drop your kit it is then available for a team mate to pick up and use. So you can go back and resupply while he does the great job of defending!!
I've got a tactic: If you're blue playing Holdout on Ghetto, just stand on the top of that damn ladder so your idiot squad actually make it to the point!
I know a very good tactic for the captain mission in carpark, but first make sure you're not the captain and that you're in the blue team... Buy a sniper, a pistol, an adrenaline shot (you know, that vaccine) and a kevlar... Go to the "tunnel" that gets you straight to the red base... Now you need a bit stealth, so dont go on wild as you usually do to kill the captain...From the end of that "tunnel" zoom in your sniper and charge it for one final blow... to the captain of course!!!Anyway, its easy, click...3...2...1...KABOOM!!!BLUE SCORES! If the captain hides near the entrance, snipe him from a distance.
TIP#1: NEVER KILL COFFEY ON YOUR WAY IF ITS NOT FOR YOUR HEALTH!!! He's gonna be a pain in the butt if he starts defending the captain, whether you kill the captain or not, you're gonna get WHOOPED!!!
TIP#2: Obviously, if the captain is not in base take your favourite weapon.
TIP#3: If you suck at sniping and lose all your bullets on 1 captain, YOU HAVE A PISTOL, which can still kill him or be your defense till you get to the loadout point.
TIP#4: You should press "V" and order your teammates to protect the captain, since you're gonna be on your way and without you they suck.
TIP#5: NEVER let Jackson defend the captain ALONE, couse you're gonna regret you set him to defend.
-----------------------------these tactics were given in this forum so far----------------------------------------------
now a few of mine...
1.to complete your missions,it is not necessary to stick to 1 team only
2.take red team in rail querry in ctf,detonation,captian ,safecracker coz when u need to enter the blue base then you can pass thru the widow by jumping!
3.take blue team in hydro in ctf,detonation,captian,safecracker coz red base is open
4. use sniper rifle in polar in captian,safecracker,get in a buggy or the 2nd lightest and fastest vehicle,drive up on to the top of the hill near the opponents base beneath which the tunnel passes(u can do that!!!) and snipe off their captians/safe

in airport captian,team deathmatch,use sniper/rocket launcher and go to the middle(made up of cement) of the place where two roads lead to the cantre part of the map and shoot from there .
5. in airport holdout,use assult rifle and wait at the top of the place near the holdout point
6.in ghetto in ctf,if u choose the blue team,then u can try taking a sniper and using the tunnel which leads to the back of the red base....the tunnel starts on the left of the enterance of red base behind a wall with an opening
7.especially in ctf,safecracker it is a better idea to run/drive away after u hav got the flag
8.use the heavily armoured tank in detonation,ctf,safecracker and u can use it to run over your enemies also
9.in trailer,after capturing the trailer,just keep driving
10. in dockyard in detonation,ctf,safecracker u can use both teams but i prefer the blue one.
if u take blue team in safecracker,u can blow up their safe from a distance using a snper and climbing on top of the middle oil drum or sum big building like that.
after getting their flag/gold,u can jump off from the rooftops present at both the edges of the railings at top floor in red base,and then use syringe and then drive off
but if u take red team,u can enter blue base from ack of the ship and top of the containers also using ladders.
11.in maps like waterfront and ghetto and airport and carpark,its a good idea to set trip mines like laser beams using primary fire in close spaces,especially in holdout
i'll tell u more when i get more ideas