I have a wonderful gadget that my daughter got me at a garage sale. It is a huge huge piece of cardboard, that folds right up when not in use. It has a grid on it, so when i am finished making my quilt top, i lay it out on that before sandwiching it, and if there's any waves in my edges, they get trimmed off right then. Then i sandwich and pin my quilt. Then, i used to quilt from the centre out, and always, the quilting would stretch and wobble my perfect edges. So now, first thing i do is stitch right around the whole sandwiched quilt first, and then i do my quilting, this ensures my quilt stays square, it also allows me to trim the excess batting off right from the start, cus i cant stand having to deal with the extra batting when trying to sew. This is the first time i've done it this way, and it's working out really well for me.