Black Ops: Team Deathmatch Tips?

Ok, so I bought black ops pretty recently. I am currently prestiged and level 36. I have trouble leveling up because I have been through much difficulty to win team deathmatch games. Some times I use the commando red dot sight and most of the time I use the famas red dot sight. I have good and bad games. My highest kill streak was only able to get me the care package. Whenever i shoot i do terrible. Someone always comes from behind... even thought i watch behind 24/7. WHOEVER ANSWERS THIS QUESTION ASAP AND ACCURATELY WITH A CORRECT SOURCE WILL BE CHOSEN AS THE BEST ANSWER AND LIKE ON MOST OF EVER COMMENT YOU POST.