Cold or warm wash , but its the dryer that really makes them shrink.

Cold wash, regular dry.

I do the same.

I started out using cold water and drying outside the dryer, but then I realized I really wasn't giving the fabric a chance to shrink or otherwise misbehave (and I wanted to know whether it would do that before I used it in a quilt), so now I use hot water and hot air.

I prewash my fabrics the same way I will wash the finished quilt. So for me, that's warm water in the wash and med/low heat in the dryer.

Since other than flannels I don't prewash...I wash my quilts in warm/warm and dry in the regular mode.