Tongue and groove flooring is milled at the edges so the boards fit tightly together as you lay them. They are generally nailed down in two different ways: First with a standard nail gun that shoots the nails through the face, then with a floor nailer that shoots the nails through the sides of the boards. You have to start with the standard nailer because the design of the floor nailer prevents it from being used right next to walls. Let the flooring acclimate to the room for a week before installation.
Cover the floor in felt underlayment, rolling it out in courses that overlap at the edges. Staple it down with a staple gun.
Lay a chalk snapline a half an inch from the starting wall, from end to end. Lay the first board along the line with the grooved side facing the wall, so there's a half-inch gap there to allow for floor expansion. Nail the board down with your standard floor nailer, putting nails through the face every foot along both edges.
Lay the next boards at the end of the first one, connecting them by their tongue and groove edging. Nail them down in the same manner. Cut the final board in the row on a mitre saw, to fit against the side wall with a ½ inch space there.
Lay the next row of board alongside the first, connecting the boards by the tongue and groove milling on the sides. Arrange them so the ends don't line up between the courses. Nail them down in the same manner, through the face.
Lay the next three or four rows of boards in the same way, until you've laid enough floor surface to bring in the pneumatic nailer. Set the nailer on the installed boards, with the front nozzle hooked out over the edge of the next board. Trigger the nailer by striking the firing pad with your mallet, to drive the boards tightly together as it shoots in the nail through the side of the board, just above the tongue.
Build across the floor course by course with the pneumatic nailer, staggering the boards between courses and cutting the end boards as needed.
Return to using the standard nail gun when you are near the far wall and running out of room to swing the mallet. Top-nail the final four or five courses of boards as you did the first few.
Use a table saw to cut the last course of boards so they fit along the wall with a half an inch of space. The spaces will be covered by floor trim.