A lot of time, effort and resources go into creating and purchasing an upholstered piece of furniture. Under all of my cushions I keep a small, white terry towel laid flat so that in the event of an accidental spill I can grab one quickly. Spills never occur when we expect or when we have something appropriate to wipe up a textile. I've seen stains on furniture that were not the result of the initial spill, but rather what was grabbed first and use to blot up the liquid.
I use these Ikea towels and at $.49 they are the perfect size (16" x 24") and the perfect price for "rags."