Visit all the local shelters. Don’t rely on a phone call. What you describe as a "medium-size yellow Lab/Spaniel mix with smooth coat" may look to a shelter worker like a "large fluffy Golden/Shepherd mix". In addition to visiting each shelter, leave a photo of your pet. Ask them if you can file a lost pet report – several of the shelters in our area exchange information so if one doesn’t have your pet, another one may. Unless you’re incredibly lucky, a single visit to the shelter won’t do. You cannot predict how far your animal might travel on it’s own, or if some well-meaning person finds your pet and takes it to a shelter across town. So check ALL the shelters on a regular basis. Go as often as you can, at least every couple of days.

Check with the highway department, your local police and the local animal control office to see whether a dead animal matching your pet’s description has been picked up. Knowing – even if it’s an unpleasant truth – is far better than not knowing

DON'T GIVE UP. Keep the faith. It is possible to locate your lost pet. Some animals have been reunited  with owners after three months, even after many months. Be diligent

Call purebred rescue groups. There a rescue group for most every breed of dog, call the All Breed Rescue Hotline, 303-989-7808. They can refer you to the appropriate organization. Hire a "pet detective". If visiting a dozen animal shelters every other day seems unrealistic to you, pay someone else to do it for you – and track down other leads too.  The sooner you act, the greater your chance for success. Check the Internet. The URL for Missing Pets Network on theSamsfan Website http://www.samfans.org/cgi-bin/statepage.pl?SA is a good start. Although it is specific to Samoyeds, there are links to several other sites that may help you recover a lost pet, for example the Missing Pet Network. Check for discussion groups that are specific to your breed where you can post information about a lost dog. The Samoyed "Samfans" were able to put together an intensive search and by working together, locate a dog that was stolen in the Pennsylvania area. "Moka" was returned, AFTER 6 WEEKS, thanks to some sharp-eyed police officers and a poster sent to the police station by a Samfan in the area.

Put up "lost pet" posters in your neighborhood or in the area where the pet was lost. Knock on doors in a two-to-four block radius to alert residents of your pet’s plight. Take the posters to vets, groomers, pet shops, and any other place you can think of where a pet is likely to wind up. Don’t forget to alert your postal carrier, the United Parcel Service and the nearest fire station. Also let the schools in your area know. Most children notice when someone in their neighborhood has a new pet. Put a picture of your pet on the poster. Simply describing the pet is not enough. Not only do people see the same things differently in terms of describing them, but assuming that the general public knows what a "West Highland Terrier", or a "Samoyed" looks like is most likely, not a valid assumption. 

Use classified ads. . Don’t make your ad too detailed. Many people may not bother calling if it seems too far away or the collar’s not the same. Recognize if you advertise a reward, you may be swamped with calls that will offer little or no hope in locating your pet - they’re interested in your money, not your pet. If your pet is returned, consider offering the finder a reward at that time.

Put appropriate ID on your pet. If that animal gets lost or ends up in a shelter, the shelter will trace the tag. A lot of private citizens will do the same. Denver area shelters are now scanning for microchips as well.