Turrets, definitely, spam the hell out of them. Want to know how i do it? I put turrets all around my base, then i slowly start creeping them into the enemies base, until the point when they come out, lead pops 'em in the face relentlessly, not to mention, it distracts them while i shoot them in the back. Instant better KDR.
Truuuuust me, turrets are the best bet. I use them alot. My arsenal for utter mayhem?
M416 CQB (perm ftw)
K5SD (perm as well, but it doesn't give you location off as often!)
Grenade or mines (sometimes flash if i feel lucky or want to piss people off)
Auto turret (My best friend :3)
Medkits (the expired.. I would love some more though! Anyone..? Awww.. ._.)