I like the controlled scrappy look, like the one in my avatar. It's got all whites and blacks in the pinwheels and brighter mediums everywhere else. (Bonnie Hunter's Patches and Pinwheels pattern, free from her www.quiltville.com website.)
I usually start by finding a pattern that I like. Then I decide on what sort of feel I want the quilt to have. Do I want a bright happy kid quilt? Or a dark masculine quilt? Or a vibrant autumnal quilt?
When I decide on that, then I can go and choose scraps and FQs and strips that fit the theme. (I have some precut strips --2 inch and 2 1/2 and 3 inch strips--, so I have a good start on cutting. That helps move the process along.)
I pull a lot of different prints. Like a couple hundred. Most of my quilts have more than 200 different fabrics in them. I just like seeing how the fabrics play nicely together. My avatar quilt has modern Kaffe Fassett and Amy Butler fabrics, reproduction prints, kid novelty prints, Asian fabric, food fabrics like cherries and berries, batiks, you name it--it's in there.
To me, more is more. And it's so much easier if you have many different prints, because it's less likely that you'll end up with patches of the same fabric in blocks right next to each other!
Good luck. Please post when you finish. I love to see scrappy quilts!