Many agents get so caught up in the online lead craze that they often overlook what some experts say is the most effective use of digital marketing: using the technology to tap existing contacts for business. First is one of the latest digital tools designed to help real estate agents sift their “sphere of influence” for clients, not just strangers who might be months out from buying or selling. Ranking leads by likelihood to move The startup — which was a runner-up at Realogy’s recent startup contest — ranks the contacts in a user’s database by how likely it deems they are to move in the next year, and it nudges agents to reach out on a regular basis and at pivotal moments. The goal is to empower users to concentrate their marketing on the contacts ripest for…