Patiently. I work in an event industry.  Sometimes potential leads just don't have projects at the time or are part of a team and they get overruled in their choice.  I usually try to keep contact every 6 months to a year in those types of leads.  They are on our email list.  Any open house events or product events we host they are invited.  If they like your business thy are possible referrals if they don't buy.