If you are stationed overseas, beware of voting deadlines creeping up. You still have time to register and vote, but it would be prudent to do so quickly. Probably the best site to handle all the stuff is
http://www.FVAP.gov, the Federal Voting and Assistance Program.
There are relaxed residency requirements if you are living abroad. You don't need to own property in the state where you will vote. However, voting is a state controlled issue, so your US embassy will not have a ballot or a voting booth for you. You will need to fill out a mail-in ballot. However, many states now will send you an email with the ballot and an envelope to put it in, which you then tape up and send. You can send it for free by diplomatic pouch at the embassy, just remember to bring your passport.
You can also get a backup federal-only ballot online. It won't be counted if you send in your regular ballot, but will be counted if your regular ballot does not arrive on time (according to my understanding).
If you know some servicemen abroad that would like to vote, please forward this information to them. There are also some other helps for warfighters stationed abroad.
God Bless