Written by the immigration attorney at law, Marisa DeFranco, ESO (not my attorney).
Original source: http://www.yourimmigrationcenter.com/cardsteps.html
In order for a non-immigrant (temporary worker) to become an immigrant (permanent worker) to work and live in the United States, they must follow these 10 steps:
Shortly after the I-485 was accepted, will you receive an invitation by the USCIS to visit your local USCIS office to get biometric data taken from you (finger prints etc.).
The Medical Exam is usually nothing dramatic. Your blood get tested (they take a little bit blood during your doctors appointment) and your general health. They check for missing immunisations depending on your country of origin. Try to get an international/multi-language version of the records for your previous immunisations to avoid getting (and pay for) shots you don't need anymore.
You can't go to any doctor you like for the examn. Only specifically approved civil surgeons are permitted to perform this check and fill out Form I-693, which will be handed to you in a sealed envelope that you should NOT open under any circumstances. The sealed envelope will become part of your Adjustment of Status fileing.
The USCIS website provides a search for USCIS approved civil surgeons in your are, which I highly recommend to take advantage of.
This step used to be just a formal step in previous years and the time between filing the I-485 and the approval of it was only a matter of weeks. The request is rarely denied and usually only in severe cases of abuse of the non-imigrant process or other major legal issues (e.g. convictions of crime etc.). Due to the shortage of visa numbers created by the fix of the backlog at the Department of Labor with the PERM and its resulting flood of applicants that moved forward in the process, can processing times take much longer. It is even strongly recommended to check the visa bulletin first to see if the adjustment of status application should be filed by people with a priority date that is yours or passed that. Why is this important?
Another Status, Another Set of Documents
Advance Parole (Form I-131 Travel Documents)
Your status changes again once you files the I-485. You can not travel anymore, not with your extension or your work visa in the passport. If you plan to travel during the time between filing the I-485 and receiving your Green Card, you have to apply to what is called "Advanced Parole" (Form I-131, "Application for Travel Documents"). Those documents will allow you to re-enter the United States during the time of status adjustment.
EAD (Form I-765 Labor Certification)
You might also want to apply for the Form I-765, called EAD. This is another Labor Certification (just like the one you already got pretty much). You need the EAD in case your H-1B or L-1 visa expires during this time. You can't get an extention for your H-1B anymore, because your changed status. Your EAD allows you to continue to work. The EAD is a special plastic card that looks like an ID and is valid for one year. It can be extended also for one year at the time, if needed.
Further Resources to the Adjustment of Status Process
This is a description of adjustment of status process in my own words. You might also want to see this article to "Advance Parole" and "EAD" and this article about the right time to file for adjustment of status (Form I-485). I found those articles at an imigration lawyers website and believe that they are easy to understand. It answered one of my questions regarding the EAD.