A good gun to use is the TAR-21. This is because stopping ower does not effect it very much and it is already very powerful. A good class is this:
TAR21 silenced
SPAS grip
Claymore
Stun Grenade(throws faster than flash)
Scavenger Pro
Cold-Blooded Pro or Hardline Pro
Ninja Pro
Killstreaks:
Harrier
Chopper Gunner
Nuke
A good game mode for getting nukes is domination. I hate saying this, but the best way to get started on getting nukes is to camp hard. Pick a good spot, and set up your claymore at any weak spots. Get a few kills, and if people start rushing you, move when the coast is clear. Once you get your harrier, find a remote spot where no one usually goes, and call it in. From there forward, just stay there and let your air support do the rest for you.