When I checked this morning, the owner had posted a notice on Craigslist, which I saw, but she didn't see mine. Little "Chocolate" found his way home. So, Craigslist is a fast way to look for your lost pets.
By msburny from San Antonio, TX
Before your pet ever escapes: Make sure they have a collar with tags! Your pet should wear an ID tag with your name and phone number. Your pet should also have a current rabies certificate; some areas may have a low tolerance for unvaccinated pets.
In the first few hours: Get as much help as possible. Call your friends and family to help you look around your neighborhood. Ask everyone you see about your missing pet. Call the local police and animal shelters to see if anyone has brought in your missing pet.
Call your pet's name as you walk around. Rattle a box of treats, or squeak a toy... anything that might get your pet's attention. Be sure to carry a cell phone with you; in case anything happens while you are searching, you can get help.
In the first few days: check with your local veterinarians and shelters every day. Don't just call! Go by in person with pictures of your pet, and to look at any pet that may resemble your pet. My Miss Bee is a Boxer/Shar-pei mix, but the last time she got out, police thought she was a pit bull. If you don't know breeds, you may call a dog or cat one thing when it is another.
Make and hang as many posters as you can. Use a good picture of your pet, and offer a reward if you choose. Put your phone number on the posters, but not your address. If anyone has found your missing pet, they can call you and arrange a meeting.
And don't ever give up hope. I recently saw a story of a golden retriever named Sam who had been adopted from somewhere in the south and transported to his new home in New Hampshire. After only two weeks, he got out and disappeared. Two years later, local animal control officers managed to catch Sam using a ham sandwich as bait and he was returned to his family. He had stayed close, surviving the cold winters thanks to kind folks who put out food and finding shelter where he could.