I use the washing machine, cold water, and little soap. Do not add fabric softener!!
I normally don't wash anything in hot, so figure why should I wash my fabrics in hot and draw the dyes right out of them. I bought some batiks from an Amish quilt shop in PA and she told me the same thing. Wash as you normally would the quilt after it is made.
I know some don't agree with this, but works for me.