Aloha.
The suggestions below are from a note I sent to someone helping me out with the eCommerce portiion of my site about how to allow multiple shipping addresses.
We sell ONE item - a proprietary book about personal finance - and offer free shipping on any quantity purchased, so the thoughts below don't cover the complicated and desireable features of calculating different rates & methods for shipping items to each address, sales tax per destination, etc.
(1) notice on buying page, both during checkout next to where shipping address is entered, and after checkout, that multiple addresses will need to be added after the transaction, or everything will be shipped to the primary shipping address. Both the "thank you" page after checkout and the confirmation email could have a link to an "enter multple shipping addresses" page requiring their order number (on the email and "thank you" page) and the various multiple shipping addresses; OR
(2) have a blank form at the bottom of the shopping cart page for special instructions and highlight that this is where extra shipping addresses should be entered; OR
(3) if more than one copy is selected, we could have one or more (depending upon the quantity of books in their cart) additional "product items" added to the cart with a flat "extra address" shipping price (in my case $0.00). Each "product item" would have a blank space in which they add an addresss to ship one or more copies to with a checkbox for "ship them all to my primary shipping address (you will enter your primary shipping address in the checkout process)"; OR
(4) we could have a "Click here if you would like to ship to more than one address (Free!)" button from the shopping cart, near the checkout buttons (regular checkout, PayPal, etc.) that would only be active if more than one copy is in cart (need to make sure of the correct order of operation between this and the upsell). When clicked, a pop-up window with forms for the appropriate number of shipping addresses could appear, starting with their primary shipping address (since their primary shipping adddress will need to be entered again later, could we populate those fields for them?; OR
(5) we could add custom fields to the shipping address page so a customer can
add as many addresses as they like.
While any of these would be a good start in terms of gathering the multiple shipping address information, there's certainly more needed at this point.
-Mark