One place to start is with reputable companies - ie larger firms. Or recommendations within your search area. My bank has a contract relocation program (lots of military customers) and I've had good luck with the realty companies they've put me with (Coldwell Banker) when I've moved cross-country. There is a certification program, and the realtors will wear a Realtor lapel pin. Your realtor should represent you, as either the buyer or the seller, looking out for your interests.