Here's the how and what to do:
(Side note: Vapor barriers are required in northern Nevada where I used to live. Even with ventilation around the foundation, the extended time of moisture on the ground due to snow allowed for moisture to accumulate and also provided a venue for radon in the soil to rise.)
Moisture Vapor Retarders/Moisture Control. In all framed walls, floors, roofs, and ceilings making up the building thermal envelope, a vapor retarder must be installed on the warm-in-winter side of the insulation, unless the framed area is ventilated to allow moisture to escape. (Vapor retarders are designed to prevent the movement of moisture-laden air from the warm side of the wall to the cool side. In temperate climates, vapor retarders are placed on the interior (warm in winter) side of the wall cavity; in hot, humid climates, they are placed on the exterior (warm) side of the wall cavity. According to the Asthma Regional Coordinating Council of New England, walls should be designed to dry to both the interior and the exterior and basements should be designed to dry to the interior. Installing vapor barriers interferes with the ability of walls to dry in both directions, so their use should be limited to severely cold climates. Paper-faced cavity insulation should be used in place of plastic interior vapor barriers.)
Foundations/Drainage. Surface water must be diverted to a storm sewer or other approved point of collection. Lots must be graded to enable surface water to drain away from foundation walls. The minimum slope away from the foundation must be six inches fall within the first 10 feet. However, if this is not possible, drains and swales may be used to ensure drainage away from the structure. (Proper drainage is important in preventing wet basements, damp crawl spaces, and possible failure of the foundation.)
edited to add link of above:
http://www.afhh.org/aa/aa_housing_codes_dry.htm