Supplies
You will need lightweight fabric, sewing thread, cardboard to shape the smocking, and straight pins. The fabric and thread should be close in color so that the thread disappears into the pleat. The fabric should be two to three times wider than your desired finished width.
Getting Started
Determine how deep you would like the pleats to be -- for example, 3/8 of an inch -- and mark rows the width of the fabric. Select a straight stitch on your machine with a 4.0 length. Be sure to have your thread on the machine before you begin. Loosen the upper thread tension on your machine and sew along the marked lines.
Completing the Pleats
Put the fabric on the smocking board (cardboard) and anchor it to the center with straight pins. Gather the lower threads carefully, gripping the fabric and pushing along the thread. Once all lower threads are gathered, check to make sure the gathers are evenly spaced, and that, when gathered, the piece is half the width of the total fabric. Use a steam iron to set the gathers, being careful to maintain their shape and width. Sew your chosen stitch below the row of straight stitching and remove the lower thread.
Tips
Make sure you have plenty of light by which to work. Spray starch and iron your fabric before you begin gathering. This will make the process easier. Ask a fabric store for the cardboard bolt from fabric. This makes a great smocking board. Good stitches for smocking are ones that sew off-center. You want a stitch that does not move the feed dogs left and right.