There are so many decisions to make when designing a house from the ground up, including things I never realized I would need to decide (like where electrical outlets would go). One reason our house works for us today is that we not only focused on style but on function. We considered the purpose of each room and expected activity when picking things like floor-tile color or the layout of our master bathroom shower.
My favorite "practical" design element is the dog door. With the addition of 12 feet of glass doors across the back of our living room, we were limited in options for allowing Trip to roam in and out of the backyard. So we did a little research and came across a dog door you can install in the wall of your house. We chose this door from PetSafe and it has worked perfectly. Because we knew going in that we would want to have it in the laundry room wall, we were able to work with the builder to have it installed, though the instructions seemed pretty straightforward.
Trip now has full reign of the backyard during the day, while also being able to be in the air conditioned laundry room, where his food and water are located, in addition to his crate (where he loves to hang out). It's a puppy paradise!
One note - if you do this during the building stage, be sure you know what brick you have on your house (just in case you need to fill it in when you go to sell your house at a later date).