This is for the U.K., but maybe it will be useful:
http://www.autism.org.uk/about-autis...to-expect.aspx

And here is a blog entry about getting diagnosed:
Aspie Like Me: A Diagnosis Story | Stimeyland

The process varies a lot, and I think that it is often made to be a much bigger deal than necessary. Generally, you will be asked about what symptoms, traits, characteristics, etc. you have and how they affect you. You should also be asked about developmental history. Maybe a parent or someone else who knew you as a child will be consulted for their input. Sometimes written questionnaires that you take home and bring back might be used. And there are various tests and inventories that help to narrow it down also.

My diagnosis was not that formal. I had seen this particular psychologist several times and others before had dismissed my reports about autistic spectrum symptoms, but he actually listened and since he already knew me, he agreed that I have Asperger's. I went back to him again about a year later and he did more testing and still diagnosed Asperger's.