Other clients have come from telling friends I was freelancing, especially developer friends who will refer you when they're too busy to take on new work. If you have no developer friends, show up at meetups, design events, and start introducing yourself to others as a freelancer. You shouldn't start hard selling in social environments necessarily-- make authentic connections with people you vibe with so when they have some work down the line, they think of you.
For me it has boiled down to what is effectively networking, though the term/concept as I understood it from afar always made me nervous and misanthropic.
Its essential for freelancers, though.
I watched a lot of Ramit Sethi videos on youtube about social behavior in negotiations, networking, and how to not being a weirdo in otherwise anxiety producing environments. These helped immensely. And the amount of free info is amazing.
Money in the bank: http://www.youtube.com/watch?v=Yb03mTqI2Io&feature=c4-overvi...