The small screws used to secure kitchen cabinet door hinges to the face frames of cabinets often work their way loose over time. Unless they're tightened immediately, the screws will enlarge and strip the holes until it's impossible to tighten them. A quick, convenient cure can be found just inside one of the cabinets: toothpicks.
Remove one loose hinge screw. Dip four or five wooden toothpicks into woodworking glue and then stuff them into the hole. Break the toothpicks off at the surface and replace the screw. If the holes are larger than about 1/4 inch, pack them with wooden matchsticks dipped in glue.