Climb a ladder. Measure three inches out from the top of the wall you are attaching the partition wall to and make a mark on the ceiling. Do this on each end of the room you are splitting.
Hold a plumb bob on the mark on the ceiling. Have a partner mark the floor where the plumb bob touches.
Measure the distance from the mark on the floor and the wall. If it is greater or less than three inches, the walls you are framing off of are not plumb.
Hold a chalk line along the ceiling and snap it to connect the two marks on each side of the room. Repeat on the floor.
Lay the 2-by-4 plates on the floor. Stagger the plates so that the difference measured in step three is represented.
Measure out 1/4 inch from the ends of the plate. Mark out 15 inches from each mark for a stud. Mark every 16 inches after that for each stud.
Draw a line across both plates for the stud locations.
Stack the two plates on top of each other, on the floor by the wall. Measure from the ceiling to the plates to get the stud length.
Cut the studs to the length measured in step 8.
Lay the plates on the floor spaced to the length of the studs. Place the studs aligned with the marks on the plates.
Secure the plates to the studs using 10d nails -- hammer two nails for every stud through the plate and into the stud.
Lift the frame up with the help of a partner and move it into position on the wall. Use a sledgehammer to knock it into place if it is tight.
Check the wall frame for plumb all the way across using a four-foot level. Adjust studs if necessary.
Drive one 16d nail into the bottom plate every 16 inches, as well as up the adjoining wall every 16 inches.