What internet service are you thinking of using? The reason I ask is that if it is cellular than the modem will need to be in a location where it gets a good signal. With most cellular modems being usb devices the cellular router needs to be in the same location. I would home run all of the ethernet cables to this location. For example in the house I am building right now, I think this location is going to be the second bedroom closet. Being a finished location, I will put in a wall plate with x ethernet positions (haven't decided how many yet) and terminate them there. As I used them I will run short jumper ethernet cable between the wall plate and the router (or switch if I have to many for the router).
If it is not cellular them I would have it close to where it enters the building.
Being low voltage no real box is required just a wall plate. But you could put in a typical low voltage box for them.
One more point, with the way TVs are evolving I would put an ethernet plug at each TV location.
