My car has leather seats and a leather steering wheel, do I have to oil them or something?

I heard that leather can get dry and crack, but water is bad for it. I remember having a tan leather couch as a kid that turned black whenever water got on it and I'd get in huge trouble for even breathing wet in that thing.

Am I supposed to wipe my car down with water? Cleaning solutions? Oil? Do I take it to a professional and is it worth it? How do I know what products are safe to use in my car? What ingredients do I avoid?