Hi Fan!! My preference is to put the sides on first, then the top and bottom. I think it just looks "right" to me that way. Also, don't worry if you have to piece the borders - with a print it won't hardly show, and no one cares. I also measure my quilts, but only through the middle side to side and from top to bottom on the right and left sides, and then check the measurements through the top part side to side and the bottom side to side to be sure I am not off a lot. After some experience you'll find that your quilts will be very close to "square" (not literally square, but measuring the same). Good luck!!