How do you go about finding new work remotely? Is it primarily return business from previous clients?

Return business is primary, yes. There's standard networking things like building a blog and being friendly, but also nonstandard networking: http://push.cx/craftsmanship-calendar

That calendar is way out of date now (it's on the TODO list to update tomorrowish), but spending time programming with people has done wonderful things for my network, my skills, my exposure to tech I'd otherwise ignore, my social skills, my vertical leap...