Salt seems to attach to leather no matter where you are. Salt that is laid upon the streets to fight ice can get on your shoes or boots and leave salt marks. Sweating heavily within your leather shoes, boots or jacket can leave nasty salt rings. It is important to remove the salt as quickly as possible. The salt will dry out leather and cause it to crack. Once the leather cracks, all the elements can get into the leather and destroy it.
Mix 1 tbsp white vinegar with 1 cup cold water.
Dip a clean, soft rag into the mixture. Ring out most of the excess moisture.
Wipe the salt stains off of the leather.
Repeat as needed until the salt stains disappear.
Dry the leather. Let the shoes sit until fully dried.
Once the leather shoes are dry, you may want to add polish. The polish will help protect the shoes from salt in the future. Regularly adding polish can keep the salt away. The polish helps keep the leather moist and aids against the drying properties of salt.
Many state that alcohol is great for removing salt stains, but alcohol will dry out the leather. Alcohol can be effective, but be sure to dilute it first. As above, 1 tbsp alcohol to 1 cup cold water should be fine.