Often times leads just don't work out right away for a variety of reasons. They might not qualify, they might have decided to stay in the home for another year, etc.
Comb through your database and call all of those “lost leads” you haven’t talked to for a while. If you have an office that saves these types of leads ask your manager if you could have a list of old company leads.
Call to say hello. Here's an idea for a Conversation Starter and Ender:
“Just checking in to see how everything is going real-estate-wise. Have you given any more thoughts to (buying, selling, investing) or have your plans changed?
Thanks for thinking about that... I owe you a favor. Just let me know if you or anyone you know ever has any little real estate question and I’ll be happy to repay that favor. And when would be best for me to follow up again?"
THEN: Schedule the next follow up date in your CRM system or in your calendar!