US citizen and US green card holder have unique filing obligations, unlike citizens of other tax jurisdictions. The US imposes taxation based upon citizenship, not based on tax residency.
If elected, your first $100'800 earned overseas are exempt from income tax (For 2015; amounts change each year), unless you are an employee of the US government. Note that if you are a Foreign Service employee, and your spouse works in the local economy, the exemption still applies for your spouse; however, the calculation changed in 2006 and results in a slightly higher tax bill.
Other considerations and opportunities include the following:
For further details regarding your tax situation as a US Taxpayer living abroad, please contact us and we will gladly answer your questions.