For me, I need to find a pattern I like and then select fabric. Do you want to do a lap quilt? A bed-sized quilt? Do you generally like random patterns (or placement of objects) or are you a more 'organized' type person?
Perhaps looking through the photo section here might give you some hints or clues. Or google quilt images. Jot down or remember what type patterns/images immediately strike you as cool/neat/interesting. It could be a repeating pattern or 'sampler' type. Do you like the consistency of just a few fabrics or are you intrigued by 'scrappy'? Narrowing down some of those questions might help with deciding on your next project.