Riding bareback is also more risky without the saddle to rely on for security. I do not recommend using a bareback pad (or a blanket beneath your seat). Because bareback pads do not have any structure (as opposed to a treeless saddle) they can slip easily if you become unbalanced. Bareback pads with stirrups are dangerous and encourage poor seat position.
Starting Out Bareback
Always use an ASTM or equivalent approved riding helmet and proper footwear. You'll want to use a quiet calm horse, with smooth gaits and a healthy back. Horses with high withers can be uncomfortable to ride bareback. If you are concerned about 'certain areas' becoming chaffed take a hint from the sport of distance riding and apply an application of petroleum jelly before heading out.
Before you begin, be sure you have mastered the halt, turning, walk, sitting trot, posting trot and canter/lope in the saddle with and without stirrups. While many of us had to learn to ride bareback because we didn't have saddles, starting out with a saddle will make things easier.
Mounting the Horse Bareback
Because you won't have stirrups to use to mount up you will have to have to use a mounting block or have someone give you a leg up. Legions of us have used a handy fence rail to mount up. But it can be difficult to get your horse lined up and standing still while you balance precariously on the fence. A sturdy mounting block is safest. (The Guide vividly remembers using a patio chair, only to have her foot go through the seat--and hanging halfway on the horse with patio chair around her calf. Not a safe situation.)
Correct Seat Position
Once aboard get comfortable. Good position is the same as in the saddle. You want bareback riding to improve your riding overall, not become a way to develop new bad habits! Be aware of the alignment of your ear, shoulder, hip and heel.
Finding Your Balance
Have someone lead the horse at a walk. Have them walk forward, turn, halt and back-up so you can get used to the feeling. When you are feeling secure walking while led, take up the reins and start, steer and stop with the side-walker along for security.
Trot and Canter/Lope
Repeat the procedure at both a sitting and posting trot. Thats right; you should be able to post without stirrups--or saddle.
To canter you may want someone to lunge the horse. Keeping your balance on a relatively tight circle is a tad more difficult. But on the lunge you don't have to worry about controlling the horse and can concentrate on maintaining your seat.
Tips to Remember
Mastering the sitting trot in the saddle will help you a lot when you learn to ride bareback.. Keep your legs long and heels down. Think of letting your weight sink through your 'seat cushions' and down through your legs. Keep those 'seat cushions' springy. Stay relaxed and flexible and don't forget to breath. Holding your breath keeps your weight high.
If you start to loose your balance don't clench with your legs. Your horse could understand this as a cue to move forward more strongly. It's fair to use a hank of mane to steady yourself at first. I think that a handful of mane is more secure than using a neck rope or strap because there is no chance of the horse's mane slipping side to side!
Many people have a tendency to lean back and let their legs push forward. Or they hunch forward and bring their heels up. Either tendency will erode your overall security and skill.
Outside the Arena or Ring
When you feel balanced and in control you can head out on your own. You should stay in the ring or arena or small fenced paddock until you feel completely confident at all gaits. When you become very good at riding bareback you might want to try riding out on trail. If you do however, consider how you will get back on if you have to dismount.
Going up steep inclines can be a challenge without a saddle. Lean forward to get your weight off of the horse's back and use handfuls of mane to prevent sliding backwards. Whatever you do don't use the reins for balance. That will confuse and hurt the horse.