Loose ends sticking out of the back look ragged. Knots make the piece lumpy. Therefore, here are two methods of starting and finishing a row of cross stitches. If you are going to use the same threads a few holes away, there is no need to cut off the ends. Leave it were it is and run it under the few stitches to the next starting point.
When you sew with two strands of the same floss, fold a strand in half, put the two ends through the needle, leaving the loop on the long end. Bring the needle up from the bottom and make the first half cross stitch. Then you go through the loop behind at the end to make a nice firm anchor before you make the second half cross stitch.
With one thread, or two different colors, turn the fabric over and run the floss under five to six stitches next to your first hole for sewing pulling gently until the ends disappear, then come up to do your first cross stitch.
To finish, pass the thread under five to six stitches at the back immediately next to the last cross stitch, and cut off close to where the thread comes out. :victory: