I am engaged to an American woman and we plan to marry in France and to live there for at least one or two years. What do I have to do to obtain my Green Card? What will happen when we will move back to the States? Will I be allow to work?
Thank you very much.

Hi,
well you won't need a green card until you plan to move to the USA.
If you are going to get married in France and will live there for a while (I would advise 2 years or more, you will see why later) then just apply for the green card about 6 months before you are ready to move to the USA.
The green card is essentiallya permanent residence card (carte de sejour en france) and therefore you dont need one if you don't live in the USA. Moreover, once you get approved, you have to move to the USA within a year, after that it is lost.
(you only get the actual green card, after passing the border, applying for it at customs, and then through the mail a couple months later)
With a green card you will be able to work, live in the usa etc.. but you will not be able to leave the country for more than 6 months without applying in advance for a re-entry permit. Otherwise you will forfait your green card.

Also, if you are married for less than 2 years when you apply, you will have to reápply (more of a confirmation...) after 24 moonths, to get the permanent card for 10 years.Therefore, if you are going to be in France for a while, wait a ocuple years,... that will mean only one application..

Good luck and dont forget to get all marriage paperwork translated in english as you go... it makes it easier.