Saddling your horse correctly is simple. Unfortunately, if you're a horse, there are a lot of things that can go wrong and make it an unpleasant part of a day's ride.
Every horse will puff out their chest and tense their muscles against the tightening of a girth or cinch. Many horses are 'cinchy' - meaning they'll put their ears back and act like they'll nip you when you start the saddling process. This is usually because a rider pulled the girth really tight all in one big pull. This is more common with a Western saddle because it's easier to tighten than an English girth.
There's nothing you can do right away to convince your horse to quit dreading being saddled. If you follow a few simple and humane procedures, your horse will eventually relax more although those ears will probably always get pinned at least a little. Horses have long memories. Give him a pet and a treat to teach him being saddled is ok. Even if he acted up when you saddled him, reward him because after all, you did get the saddle on.
Before saddling, make sure your horse's back, belly and the area just behind his elbows is clean. A chunk of mud or a burr caught in their coat will rub and hurt. Your saddle pad also needs to be as clean as possible. Sometimes they can pick up bits of shavings or burrs if they get dropped on the ground or aisleway of your barn.
If your saddle fits correctly, your pad doesn't have to be real thick. It's purpose is to protect your saddle from sweat and dirt. I have found that using a very thick pad makes it really hard to keep my saddle from slipping especially on horses who don't have well-defined withers. It pads out the wither area too much. If you need extra padding to make your saddle fit because the tree is too wide, look into getting a saddle that fits your horse better.
Horses normally get saddled from the left side. This isn't something you HAVE to do. Horses usually get used to it because people tend to always do it that way. You can easily teach your horse to be saddled from the right side - just start slow. For these instructions, I'm going to have you standing on your horse's left side.
Ok, let the saddling begin…
With a Western saddle, hook the right stirrup over the saddle horn. Have your girth either attached in the little tab on the right side or pulled across the seat. Western saddles are a lot heavier than English ones, so it's going to take a little heave-ho to get the saddle up on your horse's back. Aim to get it about 5"-6" ahead of where it will be when you ride. Now slide the saddle and pad back to the correct position with the tree of your saddle just behind your horse's shoulder blades. A tall, strong man has no problems with this at all. It's more of a challenge for gals. We just don't have the upper-body strength.
Now, walk around to the right side and unhook your girth and right stirrup. Make sure your saddle pad is in the correct position on that side - it usually slips a bit when you put the saddle on. Walk back to the left side and reach under your horse's belly to grab the end of the girth with your right hand. Tighten it up just enough to keep your saddle from sliding off if your horse moves. So it should be just barely snug.
Your stirrups should be run up the stirrup leathers before starting. Your girth should be completely unattached. If you leave it attached on the right side, it's not the end of the world, just make sure it's laying over the seat of your saddle. Set your saddle 5"-6" in front of it's normal place. Then slide it back so the tree is just behind your horse's shoulder blades. The pommel will be over his withers unless you have a saddle with a cutback pommel designed for horses with extra-high withers.
Walk around to the right side and attach your girth. Check to be sure your pad is smooth on that side while you'er there. Come back to the left side and reach under his belly with your right hand. Tighten up just enough to be snug.
Check to make sure none of the tender skin in his elbow area is pinched. If your saddle is in the right place, your girth will be in that hollow area right behind his elbow. Now just let him stand there a bit while you go get your bridle - he'll relax those tummy muscles.
Put his bridle on, then tighten up your girth a hole. Walk out of the barn - tighten up by another hole. Walk to the arena or area you'll be riding and finish tightening up your girth. It should be good and snug without being so tight as to restrict breathing. It couldn't hurt to walk a little circle with your horse just before mounting and check your girth again. A tight girth is safer than a loose one. You should be able to stand in your left stirrup without your saddle sliding. A girth that's too loose is dangerous while riding and actually can rub and irritate your horse more than a tight one.
If you're using an English saddle, pull your stirrups down just before you mount. They dangle a lot more than Western stirrups and will hit your horse's sides - sometimes pretty hard. Or, if he spins around, they can fly out and hit you!
So that's all you have to do to safely saddle your horse. Tighten the girth in many small increments - your horse will greatly appreciate that. Just before climbing on, check one more time that your girth is tight. Make sure there's no skin pinched or any burrs or dirt chunks that can rub. If your horse is notorious for blowing out his belly, check one more time while your mounted after you've walked him around for about 5 minutes to warm-up. You may need to tighten one more hole. Now go have fun.