I've learned to take a picture of my arranged blocks before sewing them together. It's much easier to see mistakes in a picture.
I've learned to not sew in the middle of the night. If I can't sleep I need to read a book or watch tv. Never sew! Especially do not cut fabric!
I've learned to put all the different fabrics for a project together with the pattern into a kit.
I've learned to cut my binding strips at the same time I cut the quilt pieces. Sewing the strips together is a good idea too.