A couple of ideas:

- Figure out how to target the people who are immediately looking for your service or might be. For the home example, people going to open houses, people searching mortgage rates, renters who just had a kid or got married, Employees of a startup that just IPO'd or was acquired.

- Try to get referrals from happy past customers. I've used home buying services and also recruiting services that will just straight up mail me a check for thousands of dollars if I was a customer, and sent them a friends referral.