OK I figured it out.
When you pick a number (0-4) thats how many squares around it that it chooses, each of those new numbers picks another square equal to the number shown. It CAN go backwards, so it can go back to the one you just chose, so if you get a 1 it can go back the way it came and lock off that area for you.
That being said, just pick any 4's and hope for the best. You get higher points when you unlock more around a number :P