There is also a great book on the subject highly recommended: http://www.triggerpointbook.com/ also available at Amazon for less.
All you need to get started is a large super ball or lacrosse ball. Using a wall or the floor start deep massage on the trigger points. Depending on the injury and history it can take days or months to completely dissolve the trigger point. It is painful (in a good way) work but well worth the effort. Best of all you heal yourself at your own rate and at no cost.
Once you have the trigger points unlocked begin a strengthening program
to prevent future injury. Keep using the trigger point therapy to keep the muscles free of pain.