I'm not sure that there is a "best way". More than likely they're going to be upset about some part of it so be prepared for it. Remember, they've been planning for your future since you were born and you've just laid down on them one of the things that they hoped wouldn't happen...yet. Try to be understanding of this while you're asking them to be understanding of your situation. Good luck!
By the way...I HAVE been in your situation and MR. Sticky makes good points above.