Very important to identify the type of leather it is before attempting any cleaning process.
Do the 5 step leather ID process to identiy what you have.
Does it absorb moisture?
If it does:
This would indicate an aniline style leather then you need to use specific aniline cleaners rather than detergent ones. Follow this with a good leather protector which will help prevent staining and damage from body oils. Any stains that already exist on this type of leather will almost certainly not be removed by cleaning processes as they have already been absorbed by the leather.
If it doesn't:
This indicates a coated/finished leather and should be cleaned with a water based foam cleaner followed by a protector.
The smoothness of the leather is no indicator of type as most grain patterns are printed into the finish anyway. All leather is smooth to start with but it depend on how the tannery has finished the leather as to how it looks and feels.
If you want to telephone me to talk you through any of this please feel free.
Hope this helps
Cheers
Judyb