Ship Your Gifts Early
When shipping to an APO or FPO address, merchants recommend that you place your order at least 10 days in advance of when you want the item to be delivered. Items ordered 10 days in advance have a good chance of making it there in time.

Choose Correct Shipping Method
Packages sent to APO and FPO addresses are considered domestic shipping by the US Postal Office. Though, when sending packages, the postal class you use to send the package can have a significant affect on the delivery time.
 
First class and priority mail are transfered overseas by air and have a good chance of arriving within 10 days.
 
Packages sent as a lesser mail class will be delivered overseas via ship and will take significantly longer. Usually, on the order of 18 to 45 days.

What is APO / FPO?
This is a military designated address that allows mail to be delivered to overseas locations at domestic rates.
 
The format for a military address according to US Postal Service FAQ page:
 
Instead of a city and state, these addresses use APO (Army Post Office) or FPO (Fleet Post Office), along with "AE" (mail going to Europe, the Middle East, Africa, and portions of Canada), "AP" (the Pacific) and "AA" (for the Americas and portions of Canada). Therefore, the bottom line of overseas military addresses is: APO or FPO; followed by AE, AP, or AA; and then the ZIP Code.