Unforntunately Apple does not provide 'care and training' instructions for maintaining the cleanliness of its fine leather cases. This works:
BEFORE using the leather case (out of the box) use washed/clean hands and apply a generous coat of TLC (Tender Leather Care) LEATHER LOTION by Wilson Leather. [Note: 8oz bottle/states: 'Preserves and cleanas all smooth finished leather). Use your clean fingertips to massage the milky LTC lotion evenly onto the smooth surfaces of the leather. Don't worry about wiping up the extra uneven solution; just re-spread and even-out with yo0ur fingers. Tested in dry winter heated air (lower humidity) this will likely occur within 5 minutes. Do not apply the TLC lotion to the suade/rough inside surfaces of the case. I have not tried this but obviously the asssumed chemistry/enriching emolunts/light oils of the formla might leak from the inside case to the electronics (I just would not go there). Your done after first well-saturated application! Touchups every few days with wiping-down the smooth leather with a fine cotton cloth saturated with TLC LOTION maintains the clean/pure quality of the leather without further dirt or stain penetration and does not change the color of the bright color (tested on what I call 'Verizon Red' color Apple case).
Note-1: If your case has already been 'dirt damaged' the TLC LOTION will not remove the saturated dirt. You're SOL. Excepting if you give the Apple store manager the option of replacing your leather case with new one (upon purchase verification) you can start with simple 'salvation solution' above.
Note-2: Works equally well on the rich color-matched Apple iPad cases as well, if also applied BEFORE use.
Hopefully Apple will do there own testing and recommendations for cleanly maintaining these great richly colored leather cases in the future by boxing instructions and posting on-line. Until then, TLC LOTION on a virgin-clean leather case (first treated before use) works extreemly well Note that TLC is also is oderless and seems to be of a very fine grade/high quality (compared to several other leather conditions which I've tested (which smell of lanolin and are 'gooey'.
Enjoy your beautiful Apple leather case!
Best Regards,
Butchmeister.