Measure the length of one wall in the room. If the shoe molding is longer than the wall, then use a miter saw to cut the shoe molding so it is the same length as the wall. If one end of the molding will be in a corner, set the miter saw to a 45-degree angle to cut that end.
Place the shoe molding on the floor so it fits snugly against the wall and floor. Hammer it in place with finishing nails, inserting one nail about every 2 feet. If the floor is uneven, you may need to hammer the molding where the floor dips to keep the molding tight against the floor.
Measure the wall directly to the right of the first wall against which you installed shoe molding. If necessary, cut a piece of shoe molding so it is the same length as the second wall. Use the miter saw to cut a 45-degree angle in the molding's end that will be in a corner.
Cut along the curve of the shoe molding with a coping saw at a 30-degree angle.
Place the shoe molding on the floor against the wall, and check whether or not it fits tightly in the corner with the first piece of shoe molding you installed. If a large gap is where each piece of shoe molding meets, then use the coping saw or a file to cut out more of the underside of the second piece of shoe molding until it fits correctly. Nail the shoe molding in place using the same method you used to install the first section of shoe molding.
Work your way around the perimeter of the room to install its shoe molding. Use the same method and techniques you used to install the first two sections of shoe molding.