I like piano key borders. Make sure that you measure your quilt top through the center both ways, ease the borders in and then you won't have wavy borders.
I make my pieces varied widths, other times I make all the pieces the same width. Sometimes I just want to use up scraps, the borders are usually 4"-6"; it depends on the quilt. I sew the top and bottom borders on first and then the sides, I don't miter my borders.
Sharon in Texas
quilting since 1988