Summarize:

You can wear your fleece several times without washing it, as the fabric is durable and tough against stains.  If you over-wash your fleece, the fabric may start to pill. In addition, clean your jacket whenever it is noticeably dirty. For example, if you’ve gone on a hiking trip and got very muddy, wash your jacket as soon as you get home. You can easily wash your fleece jacket in your washing machine. If you do this, be sure to wash your jacket with similar colors. If possible, wash it with other fleece clothing. Avoid washing your jacket with other items that may cause lint, such as towels and washcloths. Do this if your tag recommends it or if you want to avoid any pilling on your jacket. Some particular fleece jackets require hand-washing because of their fabric of any dyes used. While washing your fleece by hand takes a bit more work, it is still easy to do.  While using a cold water setting with a washing machine often avoids pilling, the machine can cause the fabric to pill over time.
Wash your fleece jacket after 6-7 wears. Use the washing machine if you want a fast and easy method. Wash your fleece jacket by hand to avoid any fabric pilling.