I think most of us find work through networking where our ideal clients are, with other VAs, and through referrals - it's a bit more complicated than just scanning a job board for an open project.
In order to truly build a practice as a VA you need to start with at least the basics for getting yourself established so that when you do approach a potential client you present a polished, professional business image *and* the confidence to win their contract!
There are a few aspects you'll want to start with but I might suggest brainstorming a list of services you're qualified and skilled to offer and branch out from there.
There are lots of great and informative threads here on the boards as well that will help you as you move forward in setting up your business.
I hope that helps!

Feel free to ask questions as you read through the posts here...