Summarize the following:
Losing track of your cat can be nerve-racking.  Keeping calm will help you think clearly and make the most of your search.  Stay relaxed and look for your cat as calmly as you can to increase the odds of you finding them.  Get a flash-light to help you in your search. Think about where you last saw your cat and start the search there. Keep focused.  Search everywhere you can think to look. Search systematically.  Look in all the possible hiding spots in a room before moving to the next room. As soon as you notice that you haven't seen your cat for a while, start searching around and inside your house.  By searching your house first, you may be able to quickly find your cat and avoid searching beyond your home.  Check everywhere, even in tight or small spaces. Look behind and under furniture. If there are areas where you can't reach or see, try using a hair dryer to blow warm (not hot) air into that space. If your cat is there it might flush them out. Ask your family members if they have seen your cat. Try shaking a bag of treats to coax your cat out from its hiding spot. Call out your cat's name.  Hearing your voice can sometimes call your cat out. Listen for your cat's voice as you search to help pinpoint its location. Cats are nocturnal, so they are more likely to be active at night. You can try turning out all the lights in your house and sitting quietly, listening for any sounds of movement. If you can't find your cat during the day, you may also want to search again when it is dark outside. You can try shaking a bag of treats, but they may not hear you or be able to resist the temptation. Try finding something very fragrant, like a stinky cheese or a particularly smelly fish. Warm it up in the microwave or oven so that the smell is more pungent and carry it around the house, wafting the smell out with your hand as you search. Your cat may not be able to resist. If you have been searching, having looked everywhere you can think, then you might want to wait for a while.  Your cat may have found a hiding spot that you have missed and may just be taking a nap there.  If you can't find your indoor cat after intensive searching, try waiting for an hour before expanding the search. If your cat is hiding due to being afraid of something, your search may have caused them to stay in hiding.

Summary:
Remain calm. Search inside your home first. Search in the dark. Use a stinky treat to lure your cat out of hiding. Give your cat some time.