I generally try to come up with a cohesive design. Perhaps flowers and loopdiloops on the main body of the quilt, Stitch in the ditch between the borders, and a coordinating flower chain or free-form feathers in the borders. Sometimes I'll finish the quilt top, but then wait until inspiration strikes, or I feel my quilting skills have improved enough to try a new design. Once I find a design I like, I'll spend lots of time doodling it on paper, in the appropriate size, until I can consistently make the design or flower I'm looking for. I've also found that the designs I can most consistently do fmq on my domestic are the ones I'm best at fmq on my friend's long arm. It's muscle memory and visualizing the design as you guide either the fabric or the machine to create that design.