Call of duty multiplayer guide.
Unlockable: Killstreak Rewards You can unlock the following rewards by meeting the Killstreak requirements below:

3 – UAV (Reveals enemies on minimap)

• 4 – Care Package (ammo / killstreak air drop — can be collected by anyone)
• 4 – Counter UAV (disable enemy maps)
• 5 – Sentry Gun (airdropped)
• 5 – Predator (directed missile)
• 6 – Precision Airstrike (choose a location.

The following weapons and equipment can be unlocked by attaining the (multiplayer) levels below:

Assault Rifles
• FAMAS – Lvl. 1
• M4A1 Carbine – Lvl. 4
• SCAR-H – Lvl. 8
• TAR-21 – Lvl. 20
• FAL – Lvl. 28
• M16A4 – Lvl. 40
• ACR – Lvl. 48
• F2000 – Lvl. 60
• AK-47 – Lvl. 70
• M14 EBR – Campaign Only
• G3 – Campaign Only Submachine Guns
• UMP .45 – Lvl. 1
• MP5k – Lvl. 4
• Vector – Lvl. 12
• P90 – Lvl. 24
• Mini Uzi – Lvl. 44 Light Machine Guns
• L86 LSW – Lvl. 1
• RPD – Lvl. 4
• MG4 – Lvl. 16
• AUG HBAR – Lvl. 32
• M240 – Lvl. 52 Sniper Rifles
• CheyTac Intervention – Lvl. 1
• Barrett .50 Cal (AKA M107) – Lvl. 4
• WA2000 – Lvl. 36
• M21 EBR – Lvl. 56
• Dragunov – Campaign Only Secondary Weapons
• PP-2000 – Machine Pistols Lvl. 1
• Glock 18 – Lvl. 22
• M93 Raffica – Lvl. 38
• TMP – Lvl. 58 Shotguns
• SPAS-12 – Lvl. 1
• AA-12 – Lvl. 12
• Striker – Lvl. 34
• Ranger – Lvl. 42
• M1014 – Lvl. 54
• Winchester 1887 – Lvl. 67
• W1200 – Campaign Only Handguns
• USP .45 – Handguns Lvl. 1
• .44 Magnum aka Colt Anaconda – Lvl. 26
• M9 – Lvl. 46
• Desert Eagle – Lvl. 62
• M1911 – Campaign Only Launchers
• AT4-HS – Lvl. 1
• Thumper x2 aka M79 grenade launcher – Lvl. 14
• Stinger – Lvl. 30
• Javelin – Lvl. 50
• RPG-7 x2 – Lvl. 65 Other
• Frag Grenade – Lvl. 1
• Semtex – Lvl. 1
• Throwing Knife – Lvl. 7
• Tactical Insertion – Lvl. 11
• Blast Shield – Lvl. 19
• Claymores – Lvl. 31
• C4 – Lvl. 43
• Knife
• Ice Picks
• Smoke grenade
• Stun grenade Attachments
• Red Dot Sight
• EOTech Holographic Weapon Sight
• MARS Sight
• ACOG Sight (and various telescopic sights that are specific to certain guns)
• Thermal Scope
• Suppressor
• Grenade Launcher
• Heartbeat Sensor
• Shotgun
• Extended Magazine
• Full Metal Jacket ammunition (replacement for Deep Impact)
• Sniper Scope (will not take up an attachment slot, just like in Call of Duty 4)
• Akimbo
• Rapid Fire (replacement for Double Tap)
• Foregrip
• Tactical Knife

Best guns to use:

 M16A4        USP.45

MG4

Ranger (akimbo)                                                                          

                                                                                                                                                      
And of course you need good perks.

Best perks to use.
1.Commando is what i use but you can use any on the first perks it dosent really matter.
2. Definatley use stopping power it kills them so muck more quicker.
3.Bling is where you have two attachments on your weapon.