I have often asked that question. I see some gorgious quilts but would never have considered those fabrics as good companions when seeing them on the bolt. Honestly, I think it takes time. I started by using a print, stripe or what ever that has multiple colors and then pull the colors from that as my companion fabrics. After I got comfortable with that, I began just diving into my stash. I would pull 5 from the same color family than toss in a sharp contrast color. Whoop-dee-doo, it works! You will get more bold and couragous as time and experience passes. And (shhhhhh) just go to quilt shows and look at magazines or books and see how other use colors. They will never know that you copied their color palettes.