Just some quick tips.
When you first prestige, use stalker, quickdraw, and sleight of hand. Equip the M4, and use that for a while. Use the default kill streaks. 3,5,7 Assault.
M4 is amazing, pretty consistent gun and you drop them fast.
After getting Stalker Pro, IF YOU HAVE A PRESTIGE TOKEN, use it on Dead Silence. I did this as soon as I got the game, really saves you from people who soundwhore. I still win my gunfights even when they hear me first, but I noticed they were pre aiming and shooting me faster when I had stalker equipped since they heard me.
When you get the type 95, USE IT. Rapid fire+Red dot is all you need. Dead silence, quickdraw, and sleight of hand.
If you want to run and gun, use the PP90 until you unlock the Mp7 Then switch to that.
Play FFA, you can die 15 times! Win the game and still finish with a 2.0 K/D. I told my friend this and he brought his up from 1.83, to 2.02.
I normally go 30-2. 30-3, consistantly, most I will die is about 7 times, but it's different for me since I have excellent gun skill, awareness etc. Even in SnD I've dropped 24-0 in games.
But if you want to have a 2.0 or higher K/D Follow my instructions
P.S If you die a lot take a break, don't rush in right away. Your k/d will drop fast if you do bad, just play smart, take your time, earn those kill streaks.