I had been on an E-3 visa (similar to a H1-B but for Australians and without dual-intent), I applied for a PERM via the EB-2 category (employment based advanced degree / extraordinary ability).

I had good immigration lawyers (McCown & Evans) and the process really had only a few main steps.

1. My employer describes to the Department of Labor a position that they would like to fill and demonstrating that they are unable to fill the position with a permanent resident or citizen.

2. A process where my employer submits my resume and reference letters to the Department of Labor to show that I am an alien that could fill the position.

3. I submit an application for permanent residence and and application to adjust my immigration status (from E-3 to PERM). Because there isn't a queue in my category (for my nationality) these can be filed simultaneously.

The first two steps took about 6 months and the final step about a year.