For those of you who are finding multiplayer really difficult then I'm sure you've welcome the death streak system with open arms. You can customize your death streak by selecting 'create a class' and choosing 'death streak'. Certain death streaks are only unlocked when you reach a specific level.
The death streak system comes in to play when you die a certain number of times in a row without getting a kill.
The death streak option you start with is 'Copy Cat' which starts once you die 4 times without a kill. Copy Cat allows you to copy the class of the player who killed you; if you are only struggling up the ranks then you can use this to get yourself a loadout of higher-level weapons but if you've unlocked most of the weapons already this perk become almost useless.
Painkiller is the second option which allows you a health boost when you spawn (it's basically Juggernaught – a health extension perk from the previous Call Of Duty Games- for a limited period). While it's active Painkiller is very useful, just beware of snipers as the one-shot-one-kill rule still applies if they have good aim.
The 'Martyrdom' option will have your character drop a live grenade after you die; it also sets into action once you've died 4 times. If you're playing a Hardcore match it's only polite to tell your team mates you have this perk on, otherwise you may find yourself surrounded by angry team mates, or even dead if you're playing hard-core ricochet.
The final option is 'Final Stand' which allows you a limited bleed out time once you've been killed. You will have your pistol equipped to ward off nearby enemies and if you survive long enough you will stand back up. Final stand can be a good perk depending on how far away your enemy shot you from - if you've been shot point-blank ready yourself for a very limited Final Stand as your enemy finished you off. If you've been shot by a distant sniper on the other hand you have a better chance of surviving as you could possibly crawl to safety before they have time for a second shot. Final Stand is only worth while if you have a good reaction time - you must be ready to shoot the second you fall into Final Stand.