Lots of good tips in this article by Chris Achard.
My favorite part:
Go to the local people who you’ve met and say:
“I’m starting to look for companies who need help with [X] – do you know of anyone I should talk to?”
The phrasing of that question is important. If you just ask them if their company is looking for consultants – then you’re really limited their answers to just “yes” or “no”.
By asking if there is anyone you should talk to though – they’ll really think about other people they know as well.
Most of my clients in the past have not come directly from people I knew – but people who knew people I knew.