Regular (standard) stitching is used for permanent seams and construction details. With most fabrics 10-12 stitches per inch is fine. On our classroom machines the middle dial will be set between 2 and 3 for regular stitch length. For finer fabrics you might need 12-15 stitches per inch, and with heavy fabrics like denim and twill you will have more success with 8-10 stitches per inch.
Basting stitches temporarily hold two or more fabric pieces together until they are permanently stitched. Basting is also used on a single layer of fabric for easing, gathering and marking guidelines. Use the longest machine stitch, usually 6 per inch. On our classroom machines the middle dial is set at 4 for basting.
Reinforcement stitching gives strength to areas that will be trimmed or clipped close to the stitching. Use 15-20 stitches per inch. On classroom machines that is the setting between 1 and two on the middle dial.