but my main question is what type of qualifications do bouncers need if any? I live in Aunstralia
I'm currently working as a bouncer in Victoria (Gippsland, to be more specific) in Australia.
You will need a level two security operations certificate, which may (I'm not certain on this) need to be upgraded at some stage to a level three.
http://www.ista.com.au/prs20103-crowdcontroller.asp
This is the course I did, and at the time it cost about $600 and went for two weeks, in Melbourne.
You will then need to apply for a Crowd Controllers licence, which will cost another $300 - $400. They will help organise this for you at ISTA during the course.
Also, what do the employers look for?
Experience is always a plus.
If you are totally green, simply try to be confident and intelligent. You don't want to seem cocky, or nervous, or arrogant.
The boss will want you to be dealing with everything from mopping the floor and picking up glasses, to dealing with absolute shitstorm brawls with barstools flying, to talking down aggressive and intoxicated patrons, and everything in between.
Just plain intimidating presence (being big and muscular with a decent "mean look")?
It helps, but some of the best blokes I've worked with have been quite small and un-assuming. It's more about how you project yourself, and how you interact with the patrons than your size.
Or do they like actual martial art training?
If so, do they generally have leanings towards some martial arts over others?
Depends. The boss I currently work with appreciates that nearly every bouncer currently working for him has an extensive martial arts background, and he's seen us using it so he knows that it A) works for us and B) is unlikely to result in injuring the patrons unless there really is no other option.
As a rule, don't try to talk to much about your martial arts. If he asks why you'd like to be a bouncer, then good reasons are: The lifestyle, the atmosphere, extra cash for weekend work, etc. This is a good time to mention that you have done a bit of martial arts, and maybe that some of the guys you train with work as bouncers and seem to enjoy it. Don't set out to let the boss know you are a black belt, but if the opportunity to mention it comes up you certainly can. Just don't brag about it!
In general, it's very hard to determine how good someone will be without giving them a chance. If an employer is looking for workers, he will probably give you a trial night or two to see how you go. It's important during this trial period to not screw up too badly. A bit of nerves and unfamiliarity with tolerances (how drunk is too drunk? How aggressive is too aggressive?) is to be expected, but being afraid to back up the other bouncers in a fight, losing your temper and belting someone, dodging work or spending all night trying to pick up girls are big no-no's.
Also, use the term 'crowd controller' or 'crowdie' instead of bouncer when talking about the job to other workers or potential employers. While bouncer is still the common parlance, people prefer to hear 'crowdie' than 'bouncer'.