Alot of your older homes have Limestone steps, and also pavers. Limestone is very durable, but needs special care. Limestone over time will get etched with patina from all the rain and traffic. The Limestone can get abrasive and this will start to degrade the Limestone. So the steps will need to be cleaned with a non abrasive ph neutral cleaner.
To clean the Limestone steps is a very easy process. You will want to dilute a ph neutral commercial cleaner with water according to the instructions on the label. A good stone cleaner even a good all purpose cleaner, will do just fine. You can also use liquid detergent mixed with two tablespoons of water, and mixing it well.
Get a good firm scrub brush and dip it into your solution and start scrubbing any soil off the steps.