This photo shows a horse saddled with the saddle in the correct position on the horse’s back. This saddle is a dressage saddle with straighter flaps, but the seat and tree of the saddle are placed the same whether the saddle is an english saddle, dressage saddle, or western saddle. (The exception being a flat saddle/saddleseat saddle, which is placed father back to allow extravagant shoulder movement) The saddle should settle just behind the withers, and the flaps should not be so far forward as to inhibit movement of the shoulders.
A saddle that fits your horse correctly should, with some variation according to saddle type, appear level as this one does. Note that the pommel (highest point in the front of the seat) and canter (highest point of the back of the seat) appear level. A level saddle is important because it helps the rider be more comfortable and communicate more effecively, and it helps the horse by allowing the rider to balance instead of having their weight tilted disproportionately on to the shoulders or hindquarters of the horse.
This black saddle pad with pink trim is avaliable in our online store and one of our personal favorites.