Great tips above!! Also, if you're going to be out riding alone, let someone know where you're headed and about when you'll be back, and carry your cell phone as Anebel mentioned. That way if it's been too long after you were supposed to be back and you're not answering your cell, someone can alert the police and/or ride out with a group after you to make sure you're alright.
And wear a medical arm band, so that it just makes it easier should something happen to you while you're not with your buddies and you are unconscious, for rescuers to contact your loved ones, know where to take you/any allergies to meds you have, etc.
"The times when you have seen only one set of footprints in the sand, is when I carried you..."