I have a wonderful son who is very busy with work, his dating life, and planning his future. I heard this little tidbit this morning "MOM!!! I need you to fix my pants!!!   Well, to his credit, he did ask me to do this a few days ago, but I was busy at work and I didn't write it down.  Well, I wanted to show you a technique that a wonderful lady named Marylou taught me years ago.   I'm sure you can see the repair.  That is because I choose a thread that was a little different than what I needed to use......so that you could see it.  Don't worry, after a few washings, you will not be able to see it.  It is also very strong, and the repair will probably last longer than the jeans do. 

I have a close up of my sewing machine.  I have removed my sewing foot so that you can see the "feed-dogs"  These are the long, textured rows that help feed the material through the machine. 

Find the button/switch that lowers the feed-dogs.so that they will not touch your jeans.

Also release the pressure on the pressure foot. I moved my setting to "0".

Change your stitch to a zig-zag stitch that is between and a small and medium in diameter for your machine.  Lower your foot and begin to sew in a SLOW-CIRCULAR manner.   In this photo, the tear is repaired on the right side and is still open on the left side.

I am nearly done in this photo.  Sew all around the tear on both sides.  You are essentially are making a new fabric with your thread.  Overlap the stitching over and over.

Here is the repair. No, I won't be showing you a picture of my son wearing them.....hopefully for obvious reasons.

Here are a couple of tips.  For Jeans that are a bit faded, use a grey thread.  Otherwise choose a thread that is a bit darker than the fabric.  Also, you may need to use the 'skinny arm' part of your sewing machine to slide the leg of the pants over to access the tear.  It's actually very simple to do....just remember to go slow.