Slope the soil outside of your home away from the house, especially in areas close to your crawl space. The soil should be sloped away at about 1/2 inch per foot. That way, water will drain away from your home, not toward it.
Line your crawl space with a plastic tarp. This is only possible in a dirt crawl space. Fasten the tarp to the walls and floor with landscape fabric stakes. If any moisture gets in, remove the tarp and empty the water before the moisture seeps into your crawl space.
Install two power fans, one at each end of your crawl space. If you keep the air inside your crawl space moving, moisture will never have a chance to settle.
Repair pipe leaks that might be contributing to crawl space moisture. Pipes that can leak into your crawl space are typically located near the crawl space, below a bathroom or kitchen, or in your hot water heating line.