Jeans are great, but lets face it, you probably have at least one pair that has a hole or rip in them. If you ignore it, it will just get worse, but it is easy to fix!
Scrap of jean material (cut from an old pair of jeans)
Jean colored thread
Basic sewing machine (available at TechShop)
Step 1: Cut a patch/backer
Place the piece of material on the inside of your jeans, and pin in place from the outside.
Step 3: Darn it!
When you get to the end of the row, leave the needle in the down position, and turn the jeans around, and create a second row of stitches in the opposite direction.
Continue adding rows of stitching to cover the entire hole. You may go back and add more rows of stitching on top of what you've already done, if you feel you need to.