Design the ceiling on graph paper, working to scale for the dimensions of the room. Make the outline exact, showing any odd wall angles, protrusions or indentations or other irregularities. Experiment using 2-by-4-foot or 2-by-2-foot panels, but keep the panel mountings aligned with ceiling joists. Use a stud finder or get in an attic to locate joists.
Measure the height for the ceiling with a tape measure from a level floor, not from a ceiling, and mark the depth, at least 4 inches below the existing ceiling. Use a level to keep the line level, regardless of any ceiling or wall angles. Snap a chalk line on all four walls. Adjust the depth of the line for any special angles, such as around heating ducts or utility connections.
Nail a bottom strip or L channel along the depth line, driving galvanized nails with a hammer into wall studs. Overlap channel ends at inside corners, miter them at 45-degree angles with tin snips or a hacksaw for outside corners; experiment with scraps on outside corners, which may not be exactly 90 degrees, to get a good corner.
Stretch guide strings from wall to wall to mark spots for runners to hold ceiling panels. Drill pilot holes through the ceiling cover into the joists and install screw eyes above the guidelines, spaced according to the mounting locations on the main runner strips. Fasten L channel to a ceiling joist along a line where a second angle will be created with a lower ceiling, if making a double drop.
Cut wires, supplied by the manufacturer, 5 or 6 inches longer than the depth of the drop ceiling. Fasten one end of each wire to a screw eye by twisting it around itself about three times. Bend the loose end 90 degrees with pliers.
Set main runners in place, one at a time, with ends in the L channel on the walls. Thread the hanger wires through mounting holes in the runner, holding the runner temporarily with the 90-degree angle. Use a level to get the runner level, then secure it by twisting each angled wire around itself at least three times. Keep wire lengths the same for a flat ceiling; adjust the length to create a sloped ceiling or to work around utilities.
Remove the guide strings and install cross runners, at either 2- or 4-foot intervals. Slip the ends into slots on the main runner to secure them. Cut cross runners as needed with tin snips or a hacksaw to fit odd spaces on the room perimeter; slide these into the main runner slots and the L channel on the wall.
Install ceiling panels, starting at the center of the room and working toward the walls. Tilt a panel to fit into the opening, then let it drop into place in the angled runners. Trim panels to fit as needed with a straight edge and utility knife, cutting at an angle if necessary to fit irregular spaces along a wall. Cut panels to fit vertically for a side where a ceiling angle was changed, with one section lower to hide a utility.