The best way to be a professional photographer is to simply tell anyone who will listen that you are one.
Start one or more web sites and a blog and loudly proclaim that only professional photographers are capable of producing the goods. It doesn't really matter whether the images you post on the web sites are any good or not of course because you have the AIPP accredited logo on your web page.
At least that seems to be the approach of one that I encountered yesterday.
Being an inquisitive type I headed over to the AIPP web page and entered just about every word associated with the person, their web pages and business names through the search function on the AIPP search page.
No results found --- maybe the search function is less than optimal I thought. A quick phone call should clear that up then and after a conversation with the Melbourne office and passing on the details of the web site with the AIPP logo it turns out that the web site owner / photographer had merely "borrowed" the AIPP logo. Needles to say the logo is no longer on those web pages, somehow I don't think that the AIPP staff were very happy to see such things on the net.
So for all the aspiring pros out there, it seems that all you have to do is want to be a pro and therefore you are.
99% the truth, the first and last sentences are a little "tongue in cheek".