When sewing, never sew over an unpressed seam. Always press the seams as you go. This will make sewing easier and will improve the quality and hang of your finished garment.
Ironing is done by using a back and forth motion. Pressing is done by using an up and down motion. Ironing can stretch the fabric out of shape and cause wrinkling and puckering on finished garments. Always press.
To keep freshly pressed fabrics and garments from getting wrinkled, allow them to rest and cool down on the ironing board for a couple of minutes before moving them. If you are in a hurry or just impatient, use a fan directed at the ironing board to cool down the fabric and set the press.