Attics are generally covered in batting or blown insulation. If blown-in insulation is used, control the height or thickness of the layers so boards can by laid over top without having to compact the filler. By adding the boards, you increase storage space for items not needed often, allowing you to move those items out of the main house and reduce clutter.
Things You'll Need
Place the 1-by-6 boards down over the floor joists in the attic so that they run at a perpendicular angle to the joists. Run the boards down along the side of the attic to create the first row.
Drill 3-inch screws through the boards and into the joist where they cross over the joists. Use flathead screws to go down flush with each board's surface. Drill slowly so that you do not splinter the wood; however, if it becomes an issue, drill pilot holes first and then insert the screws. You don't have to screw them down to every single joist they cross, but you should at least attach them to the joists closest to the ends of each board, and at least one near the middle of each board.
Measure when you get to the end of the row and cut the last board to fit. Measure the board and mark it to the measurement. Use a circular saw to cut the board at the mark. Put the board in place along the row to finish it out, and attach it with screws. Repeat steps 1 through 3 for all additional rows to finish the floor.
Measure and cut boards to the length needed if you run up against an obstruction such as duct work or recessed lighting. Stop short by 12 inches of anything that could potentially cause a fire. There should already be some type of protection in place for electrical devices so that the loose insulation doesn't get near it.
Plywood is another option for attic flooring; however, it usually needs to be cut into smaller pieces to fit through the opening to the attic.