Play online and take your lumps. Computer AI is nothing like real players, you can practice for months in single player and that won't prepare you for online.
Some tips:
- Don't get angry, you will get killed, alot. But eventually it will get better. You will have small flashes of brilliance, and those moments will come more and more often.
- Don't look at, or care about your K/D ratio. Waaay to many players are obsessed with this stat. If you play regularly and start to get the hang of things you can start to look at K/D, but ignore it for now.
- Learn to mute all the retards you hear on live, and never get into a verbal altercation with them. They only exist to piss you off, don't validate their existence.
- Find a play style that suits you. Some people sprint around everywhere, some people camp in one place the entire time. Some snipe, some go room to room with a shotgun. Somewhere in all that you will need to find a balance that suits your style.
- Match your weapons and equipment to your style. If you run around everywhere, a snipe rilfe is probably not what you need. If you stay in one place all the time, try out Claymores for protection (when you unlock them). Grenades will probably work better for you than a throwing knife.
- Match your perks and killstreak rewards to your playstyle. Pick perks that compliment what you do. Runners use Marathon and Lightweight. I suggest stopping power, as it shots do more damage and you'll kill ppl quicker, very good for new players. If you keep getting killed by helicopters, try using cold-blooded to make you invisible to them.
For Killstreak rewards, I suggest using the ones that require the least amount of kills. As a beginner, your not going to be going on 11 kill streaks alot, so using an AC120 killstreak is a waste. I suggest UAV (3 kills), Care Package (4 kills) and Predator Missle or Sentry Gun (5 kills). There is also a perk that lowers the kill count needed by one, so you could earn all three of these rewards with a 4 kill streak.
- Situational awareness. This is a big one and takes time to develop, but it's really what starts to separate good players from ppl who run around and get shot. Looka t you mini-map and know where the enemy is as much as possible. I get several kills a match by looking at that map and realizing that an enemy is about to round the corner. Be aware of any killstreak rewards flying around. If the enemy has harriers in the air, you should know that before they kill you. If your team has a helicopter in the air, watch for enemies staring into the sky at it, easy pickings.
Make use of UAV's and counter UAVs. If your team has one up, watch your minimap (u should be doing this anyway). If the enemy has one up, they can see where you are so be careful and stay hidden if possible. If your team gets a counter UAV, the enemy is blind, so it's a good time to be on the move.
- Learn the enemies behaviour patterns. If you just killed a sniper in a remote location, he's probably headed straight back to that same spot. If you look around a corner, and a sniper blows your head off, dont go that way again. Try another way, and try to flank around him. Many average players play the same way and do the same things every life. If you can notice their patterns, you can take advantage.
- Move with purpose! Once you learn the maps, know where your going and why. Stick close to walls, lead your crosshairs around corners, sprint through open areas if you have to move through them. THink of cat and how it walks around, it doesnt walk down the middle of the street, it goes under cars and lays low. Get to higher ground if you can, and stay out of the lowlands.
- Know the chokepoints and hotspots. This is another one that takes time, but once you know the maps, you will know which areas usually have enemies and which dont. You will also learn the exact locations of windows and doorways that enemies hang out in. When a good player rounds a corner, their crosshairs are already pointed at the window or doorway where an enemy is likely to be.
- Don't stand right in windows and doorways. I cannot stress this enough. When you stand right in a window or doorway, you stick out like a sore thumb. Stand back 5-10 feet from the window. You can still look out of it and not highlight yourself to the entire enemy team. Windows and doorways are deadly in this game.
- Watch your killcams! When you first start playing, each match you should earn the medal for 'most time spent watching killcams'. This is the greatest learning tool in CoD. You will be able to see all the dumb things you did and learn from them.
The thing is, as new player, your never going to be killing the elite players on a regular basis. What you want to do, is find the not as good players, the ones you can kill, and try to kill them as many times as possible in a match.
sorry for the book, I got on a roll! lol
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the other people that want to complain that you suck. i mute all those assholes from the get go anyway so i dont have to hear them.
! You just outlined EXACTLY how to play. funjoe, if you take 1/10 of the advice Puffa gave you'll be WAY ahead of the curve. 
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