Everyone has a favorite pair of knit pants. They are comfy yet look professional enough to wear into work at least on Casual Day, and you love the way they fit your body. However, they're about 2 inches too long. Most people cope with this issue by always wearing heels with the pants in question, but you can hem knit pants if you're careful not to stretch the fabric.
Pin the hem in place. Use plenty of pins so that you do not have to focus on holding the fold in place but rather can concentrate on getting the stitches into the pants. Place the pins vertically (perpendicular to the bottom of the pants) to hold the fabric more securely.
Hold the fabric right next to the area where you are stitching. Grasp it firmly between your thumb and index finger, but don't pull it out of the place that the pins are holding it. Your fingers should be immediately adjacent to the stitch you are about to make.
Leave your stitches slightly loose. Because knit will stretch, you will find that you can pull your stitches quite tight. However, this will cause bunching in your pants when the hem is complete. Leaving the loops a little loose will help the pants fall back into their original (but now shorter) form.
Pull lightly on the pant leg to spread out the fabric once you are done. This will help your pants expand back over the loose loops and make your hem nearly invisible.
Wash your pants before you hem them. This will prevent bunching due to shrinking.