You should use a stretch stitch when constructing garments out of stretchy fabrics, such as nylon or polyester. This will enable the seams of your garment to stretch along with the fabric without thread breakage or bunching. There are multiple types of stretch stitches, and your sewing machine may provide one or more options. The zigzag stitch is a commonly used stretch stitch. Most sewing machines, even those without many options, provide a zigzag stitch.
Ensure that your sewing machine has the correct size needle attached. For thin fabric, you should use a narrow needle. Use a wider needle when constructing a garment out of thicker fabric.
Cut out the fabric pieces of your pattern. Set your sewing machine stitch to zigzag. This is usually accomplished by turning a button to this setting. See your machine manual for more information.
Lay out the pieces of the section of your garment to be sewn, so that they face in with the edges together. Place the group in position under the foot of your sewing machine, in position under the needle for stitching about 1/4 inches from the edge. Sew the garment pieces together. Repeat the stitch about 1/8-1/4 inches next to the previous one, on the side away from the edge, for reinforcement.
Once you have sewn the seams for this section, lift the foot and the needle if necessary. Remove the garment pieces and cut the thread. Repeat this process for each section of your garment.
Buy extra fabric to allow for shrinkage and prewash the material before sewing your garment.