Depends upon what I'm doing. If I have several of the same blocks I'd cut it all out before I start and try to chain stitch as much as I could to simplify things. Some quilts call for different blocks so I'd probably do those one at a time . . . If it was a new pattern and I wasn't sure if I'd like doing the whole quilt in it I'd definitely cut scraps and try it first before cutting a bunch of new fabric.