Inspect all hinge plates for screw fatigue and separation. Relieve the load on the hinges by lifting on the door slightly and tighten any loose screws. Repair any stripped holes by removing the screw and filling the hole with wooden toothpicks. Shove the toothpicks into the hole and break them off flush with the hinge recess. Pack the hole tight and drive the screw back into the hole. The toothpicks will take all the slack out of the hole and allow the screw to bite and draw up tight.
Open the door and operate the latch. Blow any dust or debris out of the latch mechanism and observe the latch sliding in and out of the door. Lubricate with light machine oil if the latch seems to hang in its housing.
Close the door and observe how the door stop fits. Changes in moisture, changes in position from being bumped or changes in thickness due to painting can prevent the door from closing to the point that the strike is set to. Bump the doorstop with a hammer and wood block back and away from the door to relieve any tight spots. Bump carefully and slowly and work the block over the general area being adjusted. Do not over correct or correct all in one spot as the doorstop is rather delicate and easily broken. Renail the stop in its new position with trim nails and recaulk/repaint if the finish was damaged during the adjustment.
Close the door and observe where the latch hits the strike plate. Apply a small amount of petroleum jelly to the end of the latch and close the door. The jelly will transfer to the strike plate and indicate where the latch touches it. Determine if the strike plate is too high, too low or too deep. Adjust the strike plate by carving out a small amount of wood from the jamb with the chisel in the direction that the strike needs to move. Make small adjustments and reinstall the strike after each adjustment. Try to close the door after each adjustment so you do not go too far and remove material unnecessarily.