I just measure the length of each side then cut enough strips to equal that plus a few extra inches for "just in case" issues. I then sew the strips together (I cut salvage to fold) at a diagonal, then just start pinning the border to the quilt. If that seam in the border is very visable like in a light color, I try to position that to match a seam in the quilt so it kind of matches. Dark colors usually don't have this issue. Then just sew it one the two sides, then top and bottom. Then bind it. I have found that that diagonal seam helps in keeping the length of fabric from stretching to much. Just enough so it doesn't buckle or look stiff against the blocks. I have tried one long length and it just stretched to much and made the border look like it was bulky.