Here are my own tips and things that I've learnt through completing all of the other Call of Duty Games on Veteran Difficulty
-Stuns and flash-bangs are a man's best friend, always use them.
-Light Machine Guns (LMGs) are the best weapons to pick up as they shred through enemies and there always comes that annoying moment when you have to reload.
-Grenades usually get me killed more than the enemies shooting at me. Frags have an absolutely huge radius in which they explode. Stay clear of them and always throw them back as they are not cooked in single player.
-Always be cautious going around corners. Staying prone or crouched is a good idea.
-Let your team mates go first, so you can see where they are shooting etc and also they have infinite health.
-If you don't keep pushing forward you won't reach checkpoints as the enemies infinately respawn.
-Don't rush in on Veteren, you'll get nowhere.
-You can automatically lock on to enemies by pressing the aim/fire button. This is a very handy feature so use it.
-Most Important thing for me is if you are really struggling with a mission or can't get passed a certain point and you've been trying so many times turn your xbox off leave it for a couple of hours or a day then come back to it. Trying to get past a hard point on Veteran while frustrated and angry isn't going to happen. Done it so many times where I have decided to leave it and come back to it and I've done it 1st time.
I am aware that I haven't completed this campaign on Veteran yet, but I thought I'd give some pointers anyway :)
Hope this helps.