How to back stitch.

With a doubled piece of thread that is knotted, start your line of sewing 1/4 inch for both the side and end edge of the fabric (by side, I mean the edge of the fabric parallel to the stitching).

Bring the needle up through the fabric.  For your first stitch, pierce the fabric near the end (going backwards on the line of sewing) then bring it backup slightly in front of the first upward hole.  How far in front you go will create the length of your stitch.

Your next downward needle hole should be near where the first stitch started (you are going backwards again) and then you come upwards in front of the newly  completed stitch.  This looping through the fabric creates thread support on both sides of the fabric along your sewing line - similar to the 2 threads in machine sewing.  Continue this process for the entire sewing line, knotting the thread at the end.