I think a tips video would be a good idea. Here are some tips that have really helped me.
1) ADS constantly. Every time I go around a corner I ADS, ever time I go past a lane I ADS. Having stalker really helps with this as you can pretty much ADS at all times.
2) Sound whoring. Having at least stereo headphones has helped me tremendously, COD almost has its own independent audio interface, as you get so much information from just the sounds of footsteps.
3) Learning the main lanes in the maps. In most of the maps, there are main lanes where everyone goes. For instance in prison break, most enemies will run straight up the middle ridge, I can usually get 1-2 kills right off the bat on there. Then they typically move to the second higher ridge. I will usually switch between these 2 places on that map.