Calling out to the GB community here. 
 
I've unlocked all three rocket launchers, including the one using target guidance, and I'm just having no luck hitting those bastard helicopters. I must be using the wrong technique or the wrong type of launcher, because I'm just finding it impossible to score hits.
 
Have any of you pros in the community got any advice to give on this? What am I doing wrong?

This has been pretty annoying for me too. Best chance I can see is to hope the chopper comes in real low and give you a free shot

You have to GET TO DAH CHOPPA! Seriously though, did you try locking on to them?

Best practise is to either use stationary AA guns or get good at using the targeting pistol.
 
A lot of people (me included at one point) don't really use the targeting pistol combined with a rocket launcher to bring down helicopters.
 
Once you get even a little good at it, you can bring down multiple helis in one round.

years of playing as Anti Tank in Battlefield 2 helped me get a good sense of rocket launchers..  all u need is practice

If you want to kill it with a rocket launcher and do not have access to any anti-aircraft guns in your area, then I suggest the remote rocket launcher.
 
However, there is a trick to using it effectively. Instead of aiming down the scope - free-fire it instead and then basically guide it through tiny flicks of the analogue stick. Not the most accurate way to bring one down but I've taken down a lot of them using this technique. I tend to have the mindset of Goku from Dragonball Z guiding a spirit bomb attack when I fire it lmao

" You have to GET TO DAH CHOPPA! Seriously though, did you try locking on to them? "

" @ISuperGamerI said:

" You have to GET TO DAH CHOPPA! Seriously though, did you try locking on to them? "

You can't lock onto helicopters in Bad Company 2. "

Tracer dart + Gustav

Mounted turrets own helicopters.

" @ISuperGamerI said:

" You have to GET TO DAH CHOPPA! Seriously though, did you try locking on to them? "

You can't lock onto helicopters in Bad Company 2. "

Thanks, guys. I'm going to have to try the tracer dart + RPG combo.

Yeah, like people have said, the tracer dart + rocket or stationary AA turrets are the only reliable ways of taking them down.

I tell them depressing stories about thalidomide babies. That really brings them down.

Easy way - get into a stationary machine gun and shoot the heli down with those big bullets 
 
If you want to use the rockets, you can shoot at it straight without a tracer dart, but you have to target way ahead of the chopper or wait for it to somewhat stop from moving around and at low altitude.  Usually that happens when it's trying to hover down or changing direction.  But shooting it directly has a low success rate and can be easily avoided.  I suggest you use the gustav for this.
 
To make a sure shot, the best way is to use the Tracer Dart, but shooting the chopper with this also needs practice but it's somewhat easier than shooting it directly with a rocket since the dart is quite faster.  If you successfully hit the chopper with the dart, then target it with your gustav or RPG and wait for the square thing to stop blinking, then fire away! :)

" I tell them depressing stories about thalidomide babies. That really brings them down. "

" I've hit them with a tracer lots of times but I never figured out how to lock-on to it.
 

@buzz_clik

said:

" I tell them depressing stories about thalidomide babies. That really brings them down. "

hahaha "

Tracer darts, with practice you can hit almost every time. 

It is hard and I've only shot down a few but it's mostly about being able to judge where to aim.  You basically have to anticipate where it's going.

Having experimented a bit, the tracer dart + launcher combo is the only sure-fire way to destroy them. I can hit them 9/10 times with the tracer, and the rest is easy.

Snipe the pilot.

I like using a mounted machine gun to take down Black Hawks in rush. Against attack choppers I find it easiest to use the mounted AA gun, most pilots don't notice me/ can't hit me till it's too late.

A lot of good pilots will use the smoke perk for vehicles, they'll pop it as soon as a tracer hits and it removes it, so you shouldn't rely on it. If they're not running smoke but armour instead you can lock on easily but it will take two shots to take them down.
 
Edit: Oh, and don't try the RPG-7, use the Carl G unless you're skilled with the AT4.

I snipe the pilots.

" Tracer dart + Gustav "

" A lot of good pilots will use the smoke perk for vehicles, they'll pop it as soon as a tracer hits and it removes it, so you shouldn't rely on it. If they're not running smoke but armour instead you can lock on easily but it will take two shots to take them down.
 
Edit: Oh, and don't try the RPG-7, use the Carl G unless you're skilled with the AT4. "

" @Darksaw:  But I thought the RPG-7 was stronger against armour than the Carl G?  Also, some mad skillz in that video. :D "

Generally one person isn't going to bring them down, but fire from multiple heavy machine gun or aa turrets and other rpgs will take them down.
 
They can't dodge everything.

I've actually done a good amount of damage just firing the heavy machine guns on the first defense island on isla inocentes.

Maybe I've been doing it wrong, but how much does the tracer dart help? I tried the tracer dart +  RPG-7 AT back at launch and never got the "Locks-on from anywhere" effect from one of there promo videos and gave up on it.

You're this guy 
EDIT:damn embed isn't working and its late here's the URL:
http://www.youtube.com/watch?v=76ZBP7cY8o8&hd=1

" I snipe the pilots. "