Your tack is a serious investment, and the best way to protect that investment is to be conscientious regarding its care.  After each ride, you should wipe down your tack with a damp cloth or sponge to remove all dirt and sweat that have accumulated.  In addition to keeping your leather clean, this will give you a chance to do a safety check on your equipment after each ride.  Apply a good conditioner as necessary to keep the leather healthy and flexible (anywhere from once a week to once a month, depending on your climate and how frequently and in what conditions you ride).  Be sure to condition all the parts of your saddle that you can reach (except the billets, which should only be conditioned often enough to prevent cracking):  both sides of the flap and jockey and the panels as well as the seat.  Do a complete tear-down every month or two:  take the bridle completely apart, pull the stirrups and leathers off your saddle and give everything a thorough cleaning and inspection.  Use products specifically formulated for use on tack (I really like Effax Leather Combi for cleaning, and my new favorite conditioner is Black Country Balsam).  Do NOT use products formulated for car interiors, leather upholstery or boots, and do not use products like Murphy’s Oil soap, ammonia, bleach, baby wipes, olive oil, motor oil or petroleum jelly!

Conscientious care of your tack will add years to its useful life, and go a long way toward keeping you and your horse safe.