For a completely polished look, your pants should hit at the right length. You don't want them dragging on the ground or getting caught on your shoes. But you don't need to spend time or money taking your trousers to a tailor to get it right. If you're wondering how to hem pants, you'll be pleased to learn that it's surprisingly easy.
Start by finding a thread color that matches what was used to create the original hem. Remove that hem with small sewing scissors or a seam ripper. Next, you'll need to decide where you want your new hem to be. Put the pants on, or have the person who owns the pants try them on. Fold the pant leg up inside the pant toward your leg until it gets to the length that you want your pants to be. If you're hemming your own pants, you'll need to enlist a friend to help because, if you bend down, you'll actually alter the way the pant legs fall. Then pin the pants at the desired length, making sure they're even.
Next, take off the pants, turn them inside out, and lay them on a table, ironing board or other flat surface. Check to make sure the hems are evenly placed again by using a tape measure or ruler to see if each leg matches. Then use that measurement all the way around the leg to keep the hem even. You may also want to make chalk marks so that you can easily see a line all the way around. If you have more than two or three inches of fabric left over, trim off the excess with pinking shears to help prevent fraying.
Now you can re-hem your pants. Use a single strand of thread and make very small vertical stitches. So that your stitches don't show, be careful not to go all the way through the fabric. Also, don't pull the thread too tight, or you'll create bumps in the fabric. As you go, you want to make sure the hem lies flat. When you're done, iron the hems to complete the polished look. Try them on to make sure they're perfect, and you're ready to go.