There are many ways to distress fabric. Washing and drying is the most common, especially to age a right-off-the-shelf garment. A hot wash and hot dryer cycle will leave the fabric frazzled, damage the fibers little and maybe start creating pills.
For the washer, you can add strong detergents like Arm & Hammer Super Washing Soda, abrasives like salt, and add lots of fabric softeners to soften and weaken the fabric.
Ironing your garment on the highest setting can give you some subtle aging results.