Originally Posted by GUWonder

Go to www.spg.com and set your address to the same address as your friend.

Next, call SPG and ask them to pull up your account info using your account number.

Then, ask to transfer points from your account to his account by giving his account number.

At some point after the transfer is completed, change your address if you so desire. (The transfer of SPG points from one account to another is nearly instant.)