First thing is first. Most leather pieces will come with specific cleaning and care instructions from the manufacturer. It's best to follow these direction. However, those can get lost, or you may have not bought your furniture new.

-If the leather is super absorbent, you may want to consider applying a water repellent. It may alter the color of the sofa.
-Routine care involves vacuuming, dusting, and wiping the piece down with a clean cloth. This way, surface particles can't become something more serious.
-As soon as a spill happens, blot the affected area with a clean damp cloth. Make sure it is only barely wet. Too much water can make the spill worse. Remember to blot, not rub.
-Sealed leather can handle a very mild soap and water mixture.
-There are leather cleaning products out there. Just make sure not to use one that is oil-based.
-Keeping leather in good shape requires conditioning. Every six months or so, apply a leather conditioner. It will keep the leather supple, and prevent it from cracking or drying out.
-Placing the leather in direct sunlight, or close to a heating element will only speed up the drying process.