You need to use a good quality water based foam leather cleaner.
DO NOT use anything containing oils, waxes or silicones. (Most 'conditioners' contain waxes or oils) and furniture polish (pledge) contains silicones which will eventually destroy the finish on the leather.
BABY WIPES are the worst thing you can use as they will destroy the finish on your leather.
Saddle soap should never be usd on upholstery leather or garments it is meant for saddles which are very different from todays finished leathers.
A lot of leather wipes contain chemicals which will also destroy the finish or leave residues on the leather which will damage it.
Fairy liquid contains more salt these days to get dishes clean and this will break the finish down on your leather. This has been verified by the manufacturers (as with the baby wipes).
Magic Erasers should not be used unless you are going to renew the finish on you r leather. We have tested these recently and they sand away the top finish on the leather.
You should also follow cleaning with a good water based leather protector which will act like a 'scotchgard' and inhibit dirt and stains from being absorbed and make cleaning easier the next time. Conditioners are totally unnecessary and only a product push by manufacturers.
It is important to maintain a regular cleaning regime cleaning dirt off the surface regularly and inhibiting the absorption of body oils into the leather with a protector is the best way of doing this. The only 'moisturizer' a leather needs is from water.
Try
http://www.LTTsolutions.net for good advice and products