Like we needed another, but I felt the need. Mainly because I suck at this one, and I don't know why. I can't seem to win a gun fight. I always feel like i'm a 1/10th of a second too late in pullin' the trigger.
Most important of all, learn the maps. Make a private game you vs a ton of bots any difficulty. Run around the map until you know the hard points, flag locations, and all of the routes in between. Knowing alternate routes to approach, and alternates for when approach is the biggest advantage.
Second, slow down. Camping can be boring and noobish. However, it is a good strategy on capture the flag, ect. There's nothing wrong with stopping at corners and waiting for a few seconds. See if someone comes around and blast them. Don't just blindly rush around corners. Raise your sights and creep out, so if someone is there, you're ready to instantly shoot.
Go with an easy scorestreak combo. Go uav, care package, and cuav. Uav and cuav both help your team ALOT and give you a rapid reward to new points. Like stated, go engineer on a perk. Not only will you see bouncing Bettie's, clay ores, but guardians and sentry guns. Also, you can re-roll your care Packages. This is extremely useful. If your care package sucks, reroll it and you'll probably get good one. I'd gotten numerous choppers and lodestars like this.