How can a book be sent to a specific person without posting it - if it was posted it would be held for someone else as it is a wish list book!

Make sure your buddy has the book on their WL.  The EXACT ISBN that you have.  Then, you go to your buddy's wish list and click the "post this book" from there.  It will take you to the post book page and it will say "you are posting this book to XXX's wishlist" on that page.  Make sure it says that.  Then, post the book and it goes right to your buddy for them to accept or decline.

If you want to send it with DC, there is a Custom DC label option under My Account. 

If you have a book on your shelf that you want to send, go to My Bookshelf, click on the name of the book, and in the upper-right hand corner it says "Mail to a friend".

Hope that helps!