If you have recently bought a bike with a genuine Brooks leather saddle (or any other leather saddle for that matter) you need to know about treating it for a long life.
I personally recommend the Brooks product called Proofide which is pretty cheap and does a good job. It's basically just Tallow, and you may find alternatives out there that do the same thing. This is not just a leather polish or cream, its an animal based treatment to deeply feed leather to proof it and stop it drying out and cracking.
To apply proofide, get a clean, lint free cloth and follow my instructions below (these are for a NEW saddle)
1. For a brand new saddle - remove it from the stem of the bike and bring it in the house - it will be easier as the first coat will be rather heavy. Using a finger underneath the cloth, apply a thin-ish coating to the outer of the seat paying particular attention to the edges, the breathing holes and around the Brooks badge. The final finish should look shiny and almost wet.
2. Turn the saddle over and apply a LIBERAL coating of proofide to any exposed leather under the saddle. This is not essential but will not do the seat any harm. You may find areas that you cannot reach, but do your best - this coating is to protect the unfinished leather from rain spray.
3. Leave the saddle overnight to dry, refit to the bike, and buff off the outer of the seat (you need not worry about proofide applied under the seat unless it is likely to drop off or get on your clothes). You need to polish the outer away until there is no greasy-ness on the saddle.
4. The best advice is to repeat this outer treatment after one week, then after one month, then after two months. Thereafter, think about an application before the onset of each winter or if your saddle is looking dry.