Black Ops II has redefined the old Call of Duty killstreak system with the much-improved scorestreaks. Now instead of unlocking bonuses at a set number of kills, you can do so by earning score through a variety of different methods ranging from capturing objectives to destroying enemy ordinance.
If you're barely able to function on the battlefield, it's important to maximize your scorestreak progression for the lower-tier. It's going to be more beneficial for you to set up a 3-5 kill progression than one that requires 7+ kills before it even starts.
Coupled with the Hardline perk, this is probably the easiest way to rack up kills with a scorestreak. Don't deploy the RC-XD until you've unleashed the UAV Recon so you can see where enemies are hiding and drive your little buggy of death over to them. This will earn you the final kill you need to order a Care Package, and then it's all up to chance what you wind up getting. If you're lucky, it could be a far deadlier weapon than this combo alone provides.
Just because you're no good doesn't mean you should be useless to your team. This loadout will help your allies by giving them sight over the battlefield with the UAV Recon before obscuring it for your enemies with a Counter-UAV. All that support needs to be rewarded though, and if you make it past that, the Hellstorm Missile is a really fun toy to unleash on your blinded, vulnerable enemies.
You're hot shit and everyone knows, but it's time to put that effectiveness to work with a scorestreak that optimizes your raw killing potential. When you're setting out to build a scorestreak and routinely find yourself being the one with a high k/d ratio or are constantly capturing objectives, set your progressions so that it makes use of the more lethal options at your disposal.
Even though the rest of your team is constantly face-down in the dirt, there's no reason why you should walk the battlefield alone. The A.G.R. is a deadly mini-tank in the shape of a robot that can follow you around the warzone providing additional fire support while you're fighting. The Escort Drone has a similar effect, but it takes to the skies and covers all your blind spots. Once you've racked up enough kills, it's time to unleash the hounds with the K9 Unit. For some reason people just can't seem to get the hang of fending these things off and they make a nice surprise for anyone proccupied with shooting at you. Man's best friend indeed.
Should you feel more like a leader than a lone ranger, the Orbital VSAT will give your allies the best chance of picking off enemies with your help. Using the EMP Systems will mess up both the enemies' radar, and any electronic scopes they might be using which really cripples them. All that sacrifice shouldn't go unrewarded though, and so the Swarm will release a fleet of autonomous drones that will hunt your enemies to no end, leaving you time to kick back and applaud yourself for being such a great guy.