The size of spur selected depends on the length of the rider's leg and the size/shape of the horse's barrel. In general, a long-legged rider on a narrow-sidded horse usually requires a slightly longer spur shank simply in order to reach the sides of the horse. The spur should easily find the sides of the horse without causing undue contortion by the rider. Spur length and style is also determined by rider preference. A rider who is learning to use a spur can use a shorter length shank to avoid accidentally bringing the spur into contact with the horse.
Spurs should never be sharp. (Instead, consider the weight and shape of the spur.) However, even a spur that appears to be gentle can be overused or used abusively. The spur should fit within your level of riding skill.
The band of a western spur should sit just above the heel block of your boot. English spurs should sit on top of the spur rest, or along the seam of the boot if there is no spur rest. The curved end of the spur should point down. Spurs pointing up can be very severe. Spur straps should be buckled to the outside, with the excess neatly tucked or trimmed to the appropriate length.
***Western Spur - The western spur is generally characterized by wider heel bands, broad flat shanks and a wheel or rowel, sometimes quite large in size.
Western spurs are often categorized by discipline, with all-around, rodeo, barrel, roper and cutting versions, to name a few. Variations in shank length and curve include the gooseneck, where the shank curves up and over and the offset, which, like the English offset, angles toward the horse. Western spurs range from simple stainless steel working spurs to show spurs with intricate silver adornment. Many Western spurs also feature chap guards placed on the shanks or decorative jingle bobs, which dangle near the rowel. Western spurs may feature both a spur strap and a heel strap or chain in order to secure the spur to the boot, and to prevent it from slipping too low on the heel. Slip-on spurs are also available for schooling. It is not uncommon for western-style spurs to have longer shanks than English spurs, because western tack often has the effect of moving a rider's legs further from the horse. Non-roweled western spurs also exist and include a barrel racing spur with a rippled, wave-like ridge that allows easy contact without much turning of the toe.
Western spurs have broader heel bands and flatter shanks, and show spurs are often heavily adorned with silver.
Western spurs are worn near the heel of the boot and held on with a strap over the front of the rider's boot, although some also have heel strap or chain for added Stability.