well the last set is effing hard so I would just deal with the stuff leading up to that

1practice, practice, practice
2do it with someone (you can revive eachother where as solo 1 mistake and you get to restart)
3complete it on regular to get the general layout of the mission, then do it on veteran (its horrible getting 30 minutes in and not knowing the general direction guys come from and losing because of it)
4 probably most important TAKE YOUR TIME on veteran, you will die if you dont go slow
 5 take it in whatever order you want, but dont be like me where the only ones i have left are missions i hate so i dont want to do them =p

Look up guides on youtube, they help a lot.

" Look up guides on youtube, they help a lot. "

GamesRadar has a fantastic guide on it.

do the stealth levels solo 
find a bro who can shoot to do the rest

The Juggernaut levels are ridiculous, if you do the one in the favela with a human friend you can kind of hack it, there are videos on you-tube i think.  And the oilrig one you get someone to grab the 50-cal and sit at the very beginning up where the Dragonov is.  Then the other person just runs ahead and pulls them back one or two at a time then boom shoot that effer in the face.  Also, Claymores.