I've killed countless heli's with RPG's and tanks one of my favourite ways is using an AA mine to wing them before smashing them with an RPG.
This is the way. Lasers, Javelins and other lockons work fine too, if they are not 100% focused on you. Little Birds, just shoot the driver out of the cockpit, DMRs work well for this.
Lots of great advices and ways described here above already on how to take out helis and jets in BF4 !
Ultimate and a great additional factor is of course some teamwork. One Support soldier to deliver ammo and then a few committed engineers teaming up is usually all you need. Depending on the map, then a lone wolf engineer is typically not enough to take out a sneaky heli, especially if he/she is supported by a repair crew on board...
You should really visit youtube for a good number of videos about dealing with air-assets, they cover all the above posts and then some 🙂
