Vietnam Huey Kill Quick Way
I got recommended this method by a guy i work with and ive gone from 8 kills to 43 in two one hour sessions.
Any map with a Huey get in and take off and try to land it on top of a hill or an area with a clear view over the battlefield. Next swap seats to the side gunner with the best view. Tap the back button to highlight enemies and then blast away with the machine gun. You'll rack up kills really quick with this way.
Only problem with this method ive had is with people on your team getting in the Huey and taking off. Strangely ive only been killed twice by enemy fire as they seem to ignore a stationary grounded Huey.