Before starting the whole cleaning process, a good idea is to use a shoe tree in the shoe, as this will make cleaning them more manageable.
We begin with brushing off the dirt and bigger particles. Once the superficial dirt is gone, then use a slightly damp towel and get rid of other grime and marks. Once we have a semi-clean surface, we can start applying a cleaning product, like the Saphir Sneaker Foam Cleaner. This works exceptionally well on smooth leather surfaces, like calf leather, as well as for nubuck, suede and textiles. It will penetrate the material deeper and bring out the impurities, think facial cleaner. Let sit for 4-5 minutes. When the foam has absorbed the dirt, brush and wipe the shoes off.