You can always go out and buy shoe polish or leather conditioner. But if you want a natural solution, making your own isn't difficult. This recipe by Instructables user Antagonizer works well on leather, shoes, wood and lots of other materials.
The recipe calls for beeswax, which is a natural waterproofing and conditioning agent, as well coconut butter, sweet almond oil and castor oil. Combine the ingredients on the stove and pour your new polish into containers for storage.
Antagonizer notes that while this polish and conditioner were designed for leather shoes, straps, belts and buckles, he's also used it on pleather, wooden surfaces (much like this technique we mentioned before), and even canvas.
It's a lot of ingredients, and you're certainly not going to save any money on this DIY version over just buying polish in the store, but what you will get is a much higher-quality product that you can use on more things all over your home. Hit the link below for the full step-by-step guide, including ratios and cooking times.