Absentee Voting
Most Americans traveling abroad are eligible to vote by absentee ballot in local, state, and federal elections. Eligibility varies by state, so research your state's laws before you leave. Make sure to have all paperwork in order before you depart. Allow plenty of time when applying to vote absentee. Most states mail their ballots well in advance of an election (45 days prior), so be sure to allot for this, as well as for any postal delays. If you do not receive your absentee ballot in time, you may be able to vote via Federal Write-in Absentee Ballot. If you have trouble while abroad, contact the Voting Assistance Officer at the U.S. Embassy or Consulate in your host country.
To register to vote absentee, and for further details, please see the Federal Voting Assistance Program's website. The Voting Assistance Guide is very helpful and allows you to identify procedures and required documents on a state-by-state basis.