From the experts (this is copy & paste): IMMEDIATELY CHECK ALL SMALL SPACES!! Under houses, in sheds, in culverts, wells, every small space! Check in closets, under beds, behind dressers, in outbuildings. Go to the shelter IN PERSON, at least every other day. They are required to hold strays for only 3 days if there is no chip.
IMMEDIATELY cut several smelly socks into strips and hang everywhere outside. Lost dog experts also highly recommend putting the dog's bedding outside.
Create flyers, give to the mailperson, sanitation workers, vets, shelters, pin to bulletin boards at groc stores, tape to bus stops, etc.
Also, highly recommend posting to as many lost pet sites as possible. Here are some, starting with the best: PETFBI.ORG, FIDOFINDER.COM, PETAMBERALERT.COM, CRITTERALERT.COM, LOSTMYDOGGIE.COM, PETALERTUSA.ORG, PAWMAW.COM, FOUNDLOSTDOGS.COM, LOSTPETALERT.COM, ILOVEPETS.COM, MYLOSTPETALERT.COM, PETCOLOVE.COM, FINDTOTO.COM, LOST_DOG.ORG, FINDAPAW.COM
VERY IMPORTANT!!! Post to NEXTDOOR.COM & CRAIGSLIST.COM - many reunited in these free sites.
Obtain a 'Live Trap', place near where missing, but away from roads, and in shade. Put smelly dog bedding or owner's smelly socks inside, & put water to drink. Lost dog trackers highly recommend grilling bacon outdoors! They also recommend spreading Liquid Smoke around the house.
USE HASHTAGS - ex: #dachshund #chihuahua #chiweenie, etc. It will increase the odds of a reunion.