Draw a line around the perimeter of the room at the level where you want the ceiling. Use a 4-foot-level to ensure that the line is level.
Install the perimeter track for a dropped ceiling using this line as a guide. Screw the perimeter track into the wall studs using 2-inch-long screws. Be sure the ceiling is low enough to clear all of the duct work in the room. You can easily distinguish the perimeter track of a dropped ceiling from the center tracks because it is L-shaped while the center tracks are T-shaped.
Install the center tracks by setting their ends on top of the perimeter track at each side of the room. Measure the panels that you will be installing in the dropped ceiling and space the tracks accurately to accept the width of the panels. Support the centers of the tracks by extending wires upward from the tracks to the ceiling joists above them. Put a screw into the underside of the joist and twist the wire around it with a pair of pliers.
Install the cross pieces of the dropped ceiling so that their ends rest on the tracks you just installed and create a 90-degree angle. Measure these tracks so that they accept the length of a ceiling panel between them.
Install the ceiling panels by passing them up through the openings at an angle, turning them flat and resting their edges on the tracks. If you are left with odd-sized openings at the edges of the room, cut the edge panels to fit with a utility knife.