Here are the instructions for binding a quilt. I highly recommend Serging the entire edge of the quilt before adding binding. It smooths out the edges, flattens the bulk and makes the finished quilt look beautiful.
Piece all the strips together by laying them RST and aligning ends on the perpendicular. Mark from top inside corner to top outside corner. Here you can see how I leave the selvage edge out of the seams.
Sew along the marked line.
Trim the seams to 1/4" and press open.
Fold the strip in half, right side out and press along the entire length of the binding.
Mark a 12" gap on the edge of the quilt.
Align the raw edges of the binding to the edge of the front side of the quilt, leaving a 10" long tail of binding above one of the marks. (Pin or attach binding as desired.)
Sew the binding to the quilt at 1/4" seam. (I actually prefer to do a 3/8" seam when there is no piecing that would lose points.)
At each corner stop 1/4" (or the width of your seam allowance) from the end, pivot and sew directly out to the corner.
Fold the binding out away from the quilt and then back over itself as shown.
Sew from the edge of the quilt along the next side. Continue around the entire quilt, sewing down each side and repeat the last steps on every corner. When you reach the 12" gap, end your sewing.
Line up the binding tails flat over the rest of the gap. Using either a ruler the width of the binding or an unfolded piece of the binding as a guide, cut the tails on the opposite side of the ruler from where it starts, making sure to overlap the two pieces by the original width of the binding.
Unfold. Right sides together, sew the diagonal from one corner to the other as show.
Check before trimming the seam by folding the binding and making sure it lays flat over the gap. If not unpick and adjust. If yes, trim the seam to 1/4", press open, and refold the binding.
Sew the remaining binding to the edge of the quilt.
Trim the corners at a 45 degree angle, avoiding cutting the seams, to make less bulk for folding over the binding.
Press the binding flat and outwards on the front side of the quilt.
Wrap the binding around the quilt sandwich. Pin or secure as desired. Taking care to fold over the corners, tucking them as they are on the front of the quilt.
Sew down the binding to the backing. Here are three common methods for sewing binding down.
1. Hidden Hand Stitching: Use either a Ladder or Blanket stitch to secure the binding.
2. Visible Hand stitching: Use a hand quilting stitch along the edge of the binding using a heavier thread intentionally leaving it visible.
3. Machine Stiching: On the front of the quilt, stitch in the ditch along the edge of the binding, making sure it is catching the binding in the back. This works best with 2.5" binding and a 1/4" seam allowance when the binding is sewn on. Many quilters glue the binding to the back and press it into place before sewing.