Do you have properly working gutters and down spouts? Is water diverted away from the house? When gutters are not functional, water problems in basements and crawl spaces are very common. Be sure to check your gutters both in the spring and fall to keep them working properly.
Is your ground graded away from the house? Pay close attention to areas such as under decks, cantilevers etc. Reverse grades and depressions can wreak havoc on your crawl space or basement.
Once rain water is properly controlled you can then look at the need for sumps and internal water control.