Remove the old door, if needed
Measure the door opening
Check that the frame is square and plumb
Trim the door if necessary
Position the door in the opening
Insert shims around the hinge side
Mark the hinge locations
Cut hinge mortises, if needed
Attach the hinges to the door
Lift the door into place
Secure the hinges to the frame
Check the door swing and gaps
Add shims as needed for alignment
Install the latch and strike plate
Test the door for smooth opening and closing
Tighten all screws
Install the doorknob or handle
Apply trim or casing, if needed