While leather bike saddles are heavier, more expensive, and require more maintenance than modern plastic and foam saddles, many riders nonetheless prefer leather saddles due to their ability to shape to your body over time and provide a very comfortable ride. Leather saddles are generally around $100 in price but can truly last a lifetime.
Some riders who make the switch to leather saddles have an unpleasant surprise when they first get on: out of the box, a leather saddle is stiff and not very comfortable. This is because, like a baseball glove, leather saddles have to be "broken in" in order to work optimally.
Oil is the Key
The key to breaking in a leather saddle is oil. Like most natural materials, including leather shoes and wooden cutting boards, leather will dry out over time and begin to break down if it is not protected using some sort of oil.
Besides protection, this oiling process also helps break in the saddle by softening the leather and helping it conform to your body. When you first get a leather saddle, it is best to use some sort of leather-specific oil (such as Brooks Proofide) to rub into the leather. Rub a small amount all over the upper surfaces of the saddle.
Over time -- usually some 200 - 300 miles -- your saddle will stretch, becoming softer and more pliable in the areas which contact your body. This will provide the most comfortable ride available.
Leather saddles also require a bit of maintenance. It is best to keep them dry, as water can cause problems. If you do ride in the rain, make sure to wipe the saddle dry at the end of the ride. Like with other leather products, it will greatly increase the lifespan of your saddle to rub a bit more oil into your saddle every few weeks, or as soon as it begins to dry out. With just a little bit of love your saddle will be more comfortable than you ever thought possible and will last you a lifetime.