I'm a newbie, but so far I just choose a focal fabric and then find fabrics I like to go with it. The precuts are usually more expensive than I want to pay, but the ones I have bought were not cut well and caused more work than if I had cut it myself so I didn't save any time. But I am glad there are precuts and fabric lines for quilters who want them. I've enjoyed seeing all the replies and ideas given to answer the original question.