Use a mild APC 10/1,the key to nice clean leather is to use a brush to get into the grain/texture.
I use a swissvax soft brush,a stiff washing up brush can be good on stubborn dirt,just dont push hard or it will damage the leather.

Agitate the APC and wipe away with a pale microfibre (so you can see the dirt your removing),repeat the process untill no dirt transfers onto the cloth.

You can use a " Conditioner " after but the experts say modern leathers do not need feeding with conditioners,main reason modern leathers are painted and also have a cleatcoat on top of the paint,so your not realy conditioning the leather.

Most leather conditoners contain leather essence to make the leather smell .