I read this a few weeks ago and as a new GPS user (and yes, I still have my maps in the car) I tried it out last weekend when showing homes a bit out of my comfort area. SO glad I did as I looked like I knew each and every back road like the back of my hand.
When traveling to multiple locations program in all possible destinations prior to leaving. It's so much easier than trying to add in while traveling, or between locations. If traveling out of your area and bringing your GPS with you, program in airport, hotel, restaurants etc.
Any other tips for a newbie?