Choosing fabrics with bold patterns and contrasting colors is a great way to tie together a couple of furnishings that wouldn't ordinarily "go" together, from a color wheel perspective. Funky and vibrant patterns are all the rage, and the rooms that successfully combine a variety of patterns are wonderful to be in. For example, you could reupholster your couch in a striped pattern and choose a large scale floral in like colors for your guest chairs. Then choose a smaller scale of the same floral pattern for accent pillows on the couch.
If you want to keep it simple, find a rug that has the colors you want in your room. Take heed, it's wise to choose the rug before the furnishings. You could spend an exorbitant amount of time trying to find the perfect rug to harmonize your sage green couch with your orange patterned ottoman. It's much easier to find the rug first, and then choose upholstery that matches.