Identify the problem: loose hinge, sticking door, sagging door, damaged latch, or misaligned strike plate
Tighten all hinge screws
Replace stripped screws with longer screws
Lubricate hinges and latch
Plane or sand the edge if the door rubs the frame or floor
Adjust the strike plate if the latch does not catch
Tighten or replace the doorknob or lock hardware
Shim the hinges if the door is sagging or uneven
Replace damaged hinges if they are bent or worn
Repair or replace cracked wood, broken panels, or damaged frame parts
Rehang the door if it is badly misaligned
Test the door after each adjustment
Paint or finish repaired areas if needed