Generally, the rule is to leave a quarter inch against all walls to allow for the inevitable expansion of the flooring.
However, check the installation instructions of the product -- different products expand differently, but they all will expand. You can minimize the dimensional change in the boards by acclimatizing the room by stacking your material in the room where it will be used for a couple of days.
The gap is normally covered up with a skirting board and/or quarter round. Choose the product that you like the look of. I personally like the look of a thin 3" skirt, and then add door stop (instead of quarter round) at the bottom to thicken out the base. Door stop is the same stuff that you'll see in doorways to stop the door from closing too far, mounted to the jambs, inside the opening.