Echoing everyone on the helmet of course. Cell phone on silent or vibrate with you as well. Make sure someone knows you are riding and when you left as well as an estimation of how long you'll be at the barn, that way they'll know something's up if you go past your usual time. If your horse is spooky or fresh, let him loose for a run in the indoor arena or lunge him until he's calm and not skittish. Don't take risky chances or try a higher jump than you're used to! Stick with what you know and are comfortable with, if you're nervous. Really, it should be treated as you hopefully would any ride. Riding a horse you always have to have your wits about you and be ready for the unexpected... even something as simple as a barn cat skittering out in front of you before a jump. Look around--be aware of what might set off your horse, for example the weather. Just being conscious of your horse's state and everything around you really helps. And on top of all that- try to relax! Your horse picks up on when you're nervous. If you're not used to riding on your own, at first the thought can be intimidating, but you'll see with time that common sense and basic safety is key. Happy riding!