The instructions that came with ours says:
Use a mild solution of Ivory soap and clear, lukewarm water. Apply the soap to a clean, wet sponge, then rinse well and let air dry naturally. Always try the cleaning method in a hidden area first to be sure it�s colorfast.
Never Use...
Saddle soap, abrasive cleansers, furniture polish oil, varnish, or ammonia water. The leather has already been permanently preserved in the tanning process and needs no maintenance other than the simple cleaning recommended.
Most liquids will be initially repelled by the leather, but if left to stand over an extended period of time, they will be absorbed. This is why it�s a good idea to wipe up spills immediately. If the spill is absorbed, it will dissipate over time, just as human skin will absorb and eventually diffuse stains.
I think it would be a bad idea to use steam as it can harm the tanning ingredients a leave spots... The instructions included with a White Wing Steam Cleaner clearly states: DO NOT CLEAN INTERIOR LEATHER FURNITURE WITH STEAM....