Call of Duty: Ghosts

Just like every Call of Duty campaign there are two basic rules that everyone should follow.
One - Nobody likes a hero: Don't be running around like a mad man trying to kill all of the enemies as quickly as possible just so you can move onto the next section. Depending on what difficulty you are playing you can be killed with as little as 3 shots from anyone and then you will have to repeat the same section again which will inevitably lead to you getting pissed off. Take your time and pace yourself.
Two - Sticky Aim: When it comes to campaign there is a slight attraction that you controller has to stick to enemies when you hold down the trigger. Use this to your advantage when moving around to make sure that you get the enemies that are not so visible.
Hope my tips help you! The video below is some gameplay of me doing the campaign on Veteran so you've got something to look at if you get stuck.
Good luck!