You have gathered hundreds of business cards and attended networking events.  You want those business owners you've met to send business to you.  In order to get business you have to give business.

We make business referrals all the time when we tell someone about the great movie we saw, the good restaurant we ate at last week and tell someone how good are doctor or dentist is.  We do this without giving it a second thought.  Now refer someone to the business owner you met at the networking event you attended last week.

A manager at a company said to his employees in a staff meeting, "You make me look good, then you look, then we all get to keep our jobs and get promotions, raises, and bonuses." 

If you refer enough business to someone else they will eventually refer business to you when they meet someone needing your services just like they do when they recommend a good movie.