Shirring is one of the easiest and most satisfying techniques to learn. To make a top or dress you do not need a pattern and the only stitch you need is the regular straight stitch. Shirring is simply multiple rows of stitches using elastic thread.
Please read the comment section following this post - there is additional advice and problem solving ideas. It turns out that not every machine is the same. Thank you to everyone who has contributed!
To make a shirred top:
-Measure the chest.
-Cut a rectangle of material with one side twice the length of the chest measurement (chest x2). The other side is the length of the top you desire.
Pause: To do shirring with this method I am about to describe, you want to acquire some elastic thread from your local fabric and notions store.
To use the elastic thread, wind it by hand into a bobbin and place it in your bobbin case just as you would regular thread. Do use regular thread on the top spool (in a coordinating colour, because it will be on top of the shirt.)
-Okay, now load sewing machine with elastic thread on bobbin.
-Set your stitches to wider stitch (the theory being, the wider the stitch, the tighter the elastic)
-Start your first row by placing your needle in the material (right side up) about 1 1/2" below the top of the raw edge (leaving enough room to make a hem)
-Backstitch to secure thread, and stitch your first row. Backstitch at end of row to secure.
-Start a second row 1/2" or so below (use your first row as a guide). Make sure you pull elastic and fabric taunt as you stitch subsequent rows.
-Keep stitching rows in this manner until you have the desired amount. The bobbin will need refilled a few times. If you run out in the middle of a row, just make sure you go back over the last few stitches to secure the elastic with the refilled bobbin.
The fun bit:
-Take your sheet of shirred fabric and try it on. Wrap it around your body and make sure that it will not be too small for you or too big. If it is too small, make a second shirred sheet in the same way and join them as side seams. If too big, just make where the seam should be.
-Sew up sheet into tube.
-Hem bottom and top.