[MRCLUNKER]

I am in the process of removing a driveway and garage floor. The driveway is completely removed and the garage floor is about 1/3 out. I am trying to research the process of prep & pouring cement slabs so I have some Idea of what I am talking about when interviewing contractors for the job. I have found most of the information I need on the web and forums but have found little on the prep before the pour. What do I need under the cement as far as compacting, type of dirt, sand, gravel, do I need a vapor barrier etc. I find this somewhat strange since all the sites I visit say this is the most important part of the process but none of them go into much detail. Any help would be appreciated.