I've been trying to figure out the best tactics for using a helicopter in this game (The non Attack heli kind.), As the only air vehicle with the ability to actually transport people, it is a hugely valuable tool. But it is almost always used incorrectly. Suicide runs with a heli are one of the worst offenses 
 
I see two approaches Low and Slow, and High, quick and far....
 
Most people go for High altitude and quick, constant cyclical (As in flying in circles around the target) movement because its the safe option, you are much harder to hit, but when your that high up there are serious drawbacks.

1. Its far more difficult for your gunners to target anything ,if not impossible, due to how small the enemy units are from far away, and the constant need to account for both the heli's motion and the positioning of the gun itself
2. If they do target anything only one gunner will be able to hit things because you are flying in circles around where the enemy is, so only one side of the heli is effective. If you fly down the middle of the target at high altitude, both can shoot, but the gunners cannot target much of the area below them where they are blind.
   
3. At high altitudes and far distances, you tend to drift off to the sides of an enemy base, meaning the pilot can't guarantee any non gunners will be able to jump into an area where they can be effective. For example, on Isla Innocentes, staying off to the sides will guarantee that your jumpers will end up in the water where they will get picked off one by one. This totally negates the heli's ability as a troop carrier
4. The higher up you are, the farther you have to fall incase of getting shot down, this gives the enemy a greater chance to lock onto your former heli crew's position, move to where they will land, and close in on them. 
5. Your Flying in a circle, the defender knows, your going to fly in a circle and can be prepared for that. 

1.  Rarely does a defender see such tactics coming, making it harder for them to respond, prolonging the life of your helicopter and it's crews. 
2. Your gunners effectiveness is increased so much that not only are they more able to kill enemies that fire at the heli, but also, they provide a suppressing effect on the enemy team, if anyone sticks their head out, a good gunner will make them duck again. 
3. Lining up AT4 shots is trickier because you can't stay scoped long enough to hit the heli without getting hit by the minigun. 
4. Relative to the soldiers in the base , your heli is moving alot faster up close than it would be farther out. Snipers can't pull off effective shots at the pilot.
5. Your motion is random, the defender can't expect you to go in a specific direction each time as they can when you fly circles. You can cut horizontally across the enemies base, then quickly  switch to a diagnol motion, or just stop entirely. 
6. Because your motion is random, Mounted MGs are less effective, armored MGs, can only turn within like a 120 degree radius, if something goes behind them, like your heli, they are useless, and unarmored MG's require their operator to turn constantly when the Heli passes overhead. Finally, the farther and higher a Heli is to hit, the easier it is for an MG to shoot. They have a minimal range of up and down motion. The farther you are from and MG, the wider that angle of up and down motion gets. 

I fly low and quick, I'm a very good pilot I like to do a lot of fast maneuvering. I get satisfaction in barely dodging a rocket

I actually try to mix up high and quick to low and slow just to actually give some unpredictability to the flying.  The tendency of flying low and slow is that your gunners can actually target easier, but your chopper can be easily hit as well by tracer darts and gustav rockets.  It really depends on the situation actually, if your team's tactic is to actually use the chopper as a spawn point to flank your enemies, then go high and fast first so you can easily go around the base then immediately fly low as soon as your team mates are ready to drop from the chopper (fly low to prevent your teammates from using the parachute and give away their location). 
 
But if you have squad mates in the chopper who actually is good at gunning down enemies from above, then going low and slow is a good tactic especially when your protecting an armed MCOM from being disarmed, but still, you should be able to mix it up going high and low or slow and quick for your chopper to actually survive.

I'm a style flyer and am actually pretty amazing at times. Style as in low and fast and sidestrafing and hovering and being the u-boot wolf of the skies and being all about strategy - not pure kills... and never circlestrafing baseraping no-cap spawns.
 
Love choppers. Too bad there's 2 attack choppers on most attack chopper maps. Choppers just ain't that awesome in air to air dogfights. Air to ground, that's where the fun is at. Making me feel like the the shark in Jaws. Duh duh - duh duh - DAAAAA.
 
Sad thing is, flying choppers on such maps is most fun, when my team got both choppers. And I really fucking hate chopper thieves.

I land the chopper outside the enemy base and tell my mate to go nuts with the guns - for some reason they never expect that lol 
 
After camping with the chopper however, I tend to fly low and slow...for some reason it attracts less attention. No idea why.

" I land the chopper outside the enemy base and tell my mate to go nuts with the guns - for some reason they never expect that lol   After camping with the chopper however, I tend to fly low and slow...for some reason it attracts less attention. No idea why. "

 
I'm the guy who lifts off and immediately crashes the helicopter, pisses off the other occupants, and gets angry messages about my flying skills. There's no real way to learn how to fly one outside of the multiplayer matches.

" I'm the guy who lifts off and immediately crashes the helicopter, pisses off the other occupants, and gets angry messages about my flying skills. There's no real way to learn how to fly one outside of the multiplayer matches. "

I like to hover in the enemy base while the gunners sit and pick people of, but then the gunners will randomly jump out and I'm left thinking "What the hell am I supposed to do now?"

My helicopter tactic is to spawn as an engineer with a tracer dart and an RPG.
 
Oh wait you mean how do I FLY them myself?
Usually into the ground, ass backwards.

My heli tactic is to sit in the back as an Engineer with RPGs and plenty of repair tool use. :D

Pro-tip:  Use the alternate weapons package.   You'll be able to fire flares to counter the tracer-dart-seeking rockets.

I don't. I like my fly to be inverted, but checking that box breaks the UAV look controls. So I have to choose not to until DICE realizes it's broken then put a committee together to fix it.

i fly up then down into the ground. im so bad at flying helicopters. i wish the jets would come back

I used to get into a good position in the sky and have both miniguns in a blackhawk just spray the hell out of everyone but telling them to avoid the backs of buildings so the defenders can't run into them to hide so easily. Sometimes would just park the blackhawk sideways and keep firing while having the flare package on for any tracer darts. Then depending on where my gunner told me what was happening we'd move to the next best place. Not unfair in any sense since I was actually hovering, just most people don't seem to be aware of what a tracer dart does.
 
Tracer darts now though, blessing and a curse. You hate them when in a chopper, yet will love them when you get some apache flyer who thinks he's so "pro" by trying to land on you and keep firing rockets then repeat.
 
But yeah, tip, use smoke on blackhawks for flares (which will rid you of tracer darts and jam oncoming homing rockets sort of)  and in any other chopper apart from the hind, use ALT Weapons as the gunner or pilot, your gunner gets a tracer dart if he has ALT weapons and you get a near one-hit-kill missle from ALT Weapons.

" I fly low and quick, I'm a very good pilot I like to do a lot of fast maneuvering. I get satisfaction in barely dodging a rocket "

into buildings.

I used to be a pretty garbage blackhawk pilot until I figured out 3rd person view is awesome. I can easily pull off sideways sliding and backward sliding which is so damn useful... It keeps the heli steady for the gunners while making it very difficult for rockets to compensate for your movement. Throw in the ability to climb and dive and I never get shot down.. Sadly pilots don't get any special points really... my gunner has like 4000 and I just have 1000 or something lol

"@KimChi4U said:

" I'm the guy who lifts off and immediately crashes the helicopter, pisses off the other occupants, and gets angry messages about my flying skills. There's no real way to learn how to fly one outside of the multiplayer matches. "

This.  Everytime I see a helicopter spawn, I wait for another person to get in and fly it before I get in or else it's just a waste. "

I fly by never getting in and staying as far away from all air combat vehicles as possible.

I prefer low and slow, but i like throwing in a sudden rise or drop to confuse rpgs. But there are serious weaknesses to this method. A week ago, I played a game in which one persistent pilot kept trying to fly low and slow and eject to arm the mcoms, but every time, I shot him down with my Carl Gustav. I must have got him 5 times.