I grade myself an intermediate beginner, since I have only been quilting for four years and some. I made two horribly wonky quilts that I never quilted. First was a flower basket set on point. The block was sixteen inches and somehow, after setting triangles, it turned out to be three inches off square, which was impossible. The second and most recent one was a bargello, and I know why that one was off square--I kept sewing the strips top to bottom in the same direction and it developed a big sway as I sewed on more strips--hmm, I saw a tape recently and found my error when the instructor said to sew one strip one way, then turn it over and sew the next strip to it, going the opposite direction. I measure the quilt on the floor, with a long measuring tape and the help of my DH. I measure through the middle then I use an inner small border--usually two inches and ease that to the quilt. After that, I measure again to make sure it is square, then I know that my outer border, and the quilt will also be square