What is the best way to keep water from coming through my walls into my basement?

I am a new home owner and the previous owner did not disclose water in the baement. When it rains real hard, I get water on the floor. It looks like it is coming in from different spots on the wall because the paint is getting discolored. It is a below ground basement. Would more dirt outside help more or should I have a large concrete slab put next to the house keep the water out? Thank you!!!!!