Fairly straight forward, but the amount of times people have cocked up when trying to shoot a hunter or find one at least has made me laugh so many times that I have to make some sort of tutorial about it. So here it goes:

(Note: These have all been tested on expert by yours truly)

Noticing a Hunter
The best way to notice if a Hunter is nearby is usually by hearing his loud, awful scream that he yells when he is jumping around. One of the characters (or your team mates) may also prove useful as the character will usually say "There's a hunter around", that or someone will spot it for you and shout down the voice chat, "HUNTER!"
Usually a Hunter can be spotted by it crawling around all over the place, however when a Survivor is not nearby the Hunter will not crawl and will blend in by running with the Zombies.

When a Hunter has pinned a person down
DO NOT SHOOT IT. You should only shoot the hunter if you have a clear shot at him from afar, i.e while scoped in on the hunter with a hunting rifle. Its best to run up to the hunter, and smack him off by using your melee attack. The hunter will stumble back a couple of feet, giving you the perfect chance to shoot him at. If you shoot the hunter while he is on top of someone, then the person has a mighty fine chance of being wounded from the blasts, or even worse; killed. Its best to make sure that the hunter is immediately killed after you have melee it, as it will try to jump onto the nearest target again after a few seconds of it stumbling backwards.

Mid-air Melee Attack
The Melee attack is surprisingly devastating at blocking Hunters, especially when they are attempting to jump straight at you. Usually when you see a Hunter, your first instinct is to start pumping lead straight into its body, but the Hunter can take a few hits (apart from a Shotgun up close) and will try to jump on you, leaving you absolutely helpless. To prevent this from occurring, time the movement of the Hunter and give him a good smack while he's in the air to intercept his jump attack. Again, the Hunter will stumble back and will give you a good opportunity to shoot him from up close.

Fire against Hunter
Fire does not work very well against the Hunter. As said before, the Hunter can take quite a beating before he is finally dealt with. If the Hunter is on fire while he is on top of you, then not only will he start ripping you to shreds, but set you on fire and you will start taking more damage. Save that Molotov for Zombie swarms.

Pipe Bomb
Along with every other boss, I think the Hunter is not effected by it. So don't waste it.

Pretty much it, as said before its fairly straight forward.

Just to go against what you say,

Getting a hunter off at long range crouch, wait for reticle to zoom in to max accuracy then shoot it off, for quite long ranges though.

Other wise jsut melee it off and keep meleeing it, annoying thing is your ally gets back up quickyl often in between you and the hunter causing FF hence why you should only melee it at close range, also meleeing it makes it unable to pounce for 2 seconds so keep donig itr and hes stationary and dead after 5 hits

Always against and never with hey Ares? =P
But your right, it is annoying when the hunter stumbles straight into another ally, and its best to melee him down. =)