You need to have a structural engineer look at the elevation of your property, usually need to install a sump pump.
Trenching and installing drainage tile, along with a sump pump is often protocol. Depending on what surrounds the crawl space, different solutions may be needed. If it is landscaping that is up against the house, then make sure the ground out from the house tips away and sheds water. Placing plastic under the rock, mulch, or other lens acting materials can help prevent water from penetrating the ground close to the foundation. Checking to make sure all gutters are clean and working properly is always a good place to start. If it is concrete or something else that surrounds the foundation, sometimes a special caulking is used to seal the expansion joint.