Consider that in a rain storm of one inch over 1,000 gallons of water can fall on the roof of an average home. That's a lot of water. You want to make sure it is being directed away from your home's foundation.
If your landscaping is level or grades toward your home in some areas, the rain runoff will settle against the house and seep into your foundation, either through the cement itself, or through cracks and holes in the foundation. This is an easy fix by adding soil and compacting it around the house so that the grade is about one inch per foot and extends about 6 feet from the house.
Then check if your gutters and downspouts are missing or if they are doing the job of directing the water away from the house. Downspouts need extenders or splash blocks to do the job effectively. A rule of thumb is a downspout every fifty feet of your roof line.
You have done all that and the basement still has a water problem? If you are from the DIY school, you can head down to the local hardware store and purchase some waterproofing compound. If that sounds like a daunting task you can hire a contractor to do the job for you.