I have had leather cars since I was a teen and always use Mother's Leather Cleaner and Conditioner. Available at Autozone, Advance Auto Parts or the like for around 9.99 it cleans really well (had grease stain from indy pants on sand leather seats, this took them right out on one pass) and the leather is left cleaned and soft and smelling great.

I spray it and let it soak for a minute or so then clean.