Measure the wall and transfer that measurement to the first piece of crown molding that needs to be cut. Mark a straight line across the entire piece with a pencil so that a complete cut can be made.
Turn the piece of crown molding upside down and slide it into the miter saw along the fence so that the top of the molding runs along the base of the saw and the bottom of the molding is upright on the fence.
Line up the blade to the mark on the molding. Turn on the saw and pull down on the lever to to release the guard and start the saw. Bring the blade straight through the saw to trim off the excess crown. Release the lever to turn off the saw.
Line up a protractor along the corner of the room to get the angle measurement to trim off an angle. Record the angle measurement and turn the blade of the saw to half the angle measurement in either direction. Mark on the piece where it needs to be trimmed off and repeat the cutting process from the previous step.
Turn the angle to the same degree in the opposite direction to trim off the other side and butt the two together to make sure they fit properly.