Map the damage
Look for thin cloth, loose fibres and weak areas around the hole. Extend your repair plan beyond what is immediately visible because washing and movement can reveal more damage.
Trim only loose threads that will interfere with the patch. Keep stable fibres where they can help the repair blend into the surrounding cloth.
Choose and place the patch
Use a compatible cloth with enough body to support the garment and enough flexibility to move with it. Cut a shape that reaches sound fabric on every side.
Baste or hold the patch in place before transferring the pattern. Check pocket openings, seams and the reverse so the repair does not block a function of the garment.
Build the stitch field
Begin with a simple pattern that crosses stable cloth beyond the old hole. Keep the density even and let the rows reinforce the whole patch rather than circling only the opening.
Flex and inspect the repair as you work. If the area becomes stiff or puckered, adjust the patch and spacing before adding more thread.