There is a lot to it. When I did it you had to "be absent" from the US for at least 330 days out of the year. Tax free earning were capped at 95,000. That 95,000 only includes salary. You must still pay taxes on other earnings such as rental properties, business income, and investments. If you are paying taxes to the foreign country you live in it may offset your US taxes. So lots of stuff you would probably want to speak to a professional about.