Tighten the screws on the knob plate
Remove the knob cover if needed to access hidden screws
Tighten the set screw on the knob stem
Check and tighten the latch plate screws on the door edge
Tighten the strike plate screws on the door frame
Replace stripped screws with longer screws
Fill stripped screw holes with wood filler, toothpicks, or dowels
Reinsert screws after the filler sets
Replace a damaged latch or knob assembly
Test the knob for secure operation after tightening