Alright, so I am a semi-noob myself and I figured it might help some other people to tell you what has helped me.
So I have been working really hard to just succeed in the game. I have a few things that have helped me alot.
First off... if you are new don't try and rush. If your accuracy isn't the best and you are not getting many kills, don't rush. Take your time working through the map. Take cover and try to play as tactical as possible. You will see people before they see you and it will give you more time to kill them before they kill you
Second... play on some private matches with friends. People on ipc are very willing to help if you don't have many friends that play COD. Also if you have Black Ops, play combat training. It will help with your accuracy and give you more confidence. Have your friends go a little easy on you until you get it. This will help you get to know the maps a bit more. You can also have your friends tell you where the high traffic zones are on the maps.. that helps as well.
Third... get some fps freeks if you have the money. They are 10 dollars and have helped me more than you would think. It gives you more control of your aim and will help your accuracy.
Next..Use a silencer. It will hide your location from the enemy team, therefore you will die less and get more kills.
Next..Run along the outside of the map so you dont get ganged up on as much. You might get less kills, but you will also die alot less.
Try to not panic when you are killed or someone is shooting at you. Music helps me alot. It makes me calm and from getting too aggro/ragey. The angrier you get the worse you do.
Keep your game volume up so you can hear footsteps and where people are shooting from. This will let you know where the enemys are.
Try different guns to figure out what you are good at. Go on COD elite and see which guns your accuracy is better at and use those.
You might want to pump your trigger (burst fire) so that you are not wasting ammo as well.
I'm sure there are more that I can't think of right now but I hope this has helped.