I agree with all that PaperPrincess mentioned. It makes a tremendous difference in longevity when the fabrics are prep for quilting.
One other suggestion - in our guild we have used a number of fabrics not recommended for machine washing. We in fact do take them to be laundered and use only the ones that survive. In other words, those that shred will not survive in your quilt as we all know so well, those that shrank will now no longer shrink and you can back them now with inferface and those that seem to bleed can be deleted from the pile for safe quilt making. and if you have a great piece of clothing that tends to shred a little too much for your liking but you really want to use it - wash it, back it with interface and then serge the edges to keep is from further shredding. A number of us have made quilts from family member's clothing (wool coats, ties, silk outfits, etc...) and find these tricks to be very helpful in making a quilt that will last for years.