I assume you're talking about a quilt that's already completed, rather than quilt blocks. I wash the quilt (gentle, cold water), put it on the dryer on low heat (or fluff), take it out before it is dry, put it on a sheet on the floor, and if it is out of square then I can pin it to the carpet to make it square until it dries. If it's a smaller quilt I can pin it on the design wall and accomplish the same thing. Usually just laying it out and letting it dry square (without pinning) is enough.