1: Play TDM.

2: Often go back to kill a sniper/camper that just killed u.
Just be smarter this time, and think that he might have move upwards, camping closer from ur respawn point than where he got u (some are very good at this, I do it too now) to catch u running for him when on ur way to his last known position b4 u get cautious.
Getting these campers can be real tough, and won’t help ur K/D at first but will teach u spots where u don’t wanna attack from, and spots that u want to check (and how to approach them) for killing some sniper/camper without any effort or risks, even without approaching when u’ll be better. Also when u get killed by a camper/sniper, u know where he is while ur teammates don’t (unless u tell them via comms).
Flank him, shoot a noobtube/semtex/cooked grenade in his hole, u must kill him, before he gets a nuke.

3: Circle the map.
With ur team if u’re using power perks (stopping power, danger close) or with the team but sometimes alone if using ninja (and cold blooded eventually). I only cross the map in the middle to get a “safe and sure” kill, or double kill… Then I go back where the enemy cannot come from one of my sides, on the map’s edge. (If u run fast & stealth no one will show up in ur back either…)

4: Always use NINJA pro.
Stay inaudible. No other perk gives u better advantage over ur enemy (although commando which increases the reach with ur knife is a killer perk too, but in close quarters only, and just not as precious as the total stealth advantage, I use commando only till I unlock the ninja perk).

5: Use the killstreaks mentioned by the post author.

6: After all this, u’ll often find urself with a bunch of kills but no more ammo…
Maybe it’s time to set up a few classes with ur preferred guns as a primary, and ONE MAN ARMY pro as a secondary, so u never run out of ammo, nor grenades, nor claymores, nor noobtube ammo, and u can also use power perks, and change to stealth perks class when u hear enemy UAV spotted, and then back to power perks.
Inconvenient in having “infinite ammo” that way is that ur lack of secondary or the time u need to swap classes WILL get u killed, at some point, careful.
Another cool aspect (when enemy UAV’s online) is that when u swap from UAV visible to a cold blooded class and disappear from enemy’s radar it really hits ur enemy in the mind, if u got UAV online, u’ll see some stop, some go away, some go away then come back, some come slowly, still, some just keep running straight to ur last red point.

Voila.

That’s how I did to finally kill more than I die, much more now.

We all have different gamestyles, my one is working for me now that I mastered it, the post author’s style works for him, while different (it’s a good config he has, give it a try), hope u find urs.

My babies:

Classic [excellent K/D ]: TAR21+noobtube, Claymore, One man army, Danger close, Ninja.
(I put 2 claymores here and there, use the noobtube extensively since I can reload it forever (with danger close it’s multikill after multikill) even if it’s noobish (some may call me a cheater, I invite them to fight me 1 on 1 without noobtube, PSN: Braillce), each shot gives ur position away, so I believe it’s fair, if they can’t get to me they should read this & try to get better).

Enemy UAV online [great K/D]: TAR21+noobtube, Claymore, One man army, Cold blooded, Ninja.
Same but stealth.

Silent [good K/D]: AUG BAR+silencer, Semtex, One man army, Stopping power, Ninja.
For holding a position, or for quiet & traditional hunting. Silent also great to attack groups, as it takes some time to find where are the silenced bullets coming from.

Fast [K/D just ok]: P90+FMJ, Semtex, One man army, Lightweight, Ninja.
When they play real fast.