Make sure you have money to tide you over during the lag between your last check in the states and your first check in your employing country.
Get traveler's checks to cover expenses during the last few weeks at home and the first few weeks abroad.
Keep a bank account open in the states to cover bills that will arrive after you leave and to facilitate a smoother transition upon your return.
Arrange for someone to pay your bills using your bank account.
Cancel memberships or accounts you won't be needing, or find out if you can put them on hold and extend the expiration date.
If you want to hold on to your apartment during your absence, find someone to sublet. Check your lease to make sure subletting is allowed, and sign a written agreement with the person who sublets.
Write a will, and notify someone in the states of its existence and location.
You must file a U.S. tax return each year. The Internal Revenue Service will extend the filing deadline by two months for most American citizens living abroad. If you work overseas and earn less than $70,000 per year, you do not have to pay U.S. taxes on the foreign-earned income, but still must file a return.
For more tax information, see Publication 54: Tax Guide for U.S. Citizens and Resident Aliens Abroad (for a free copy, call 800-424-FORM) or the Institute of International Education's publication, Teaching Abroad (address on page 74).