Although most people do not have the tools or equipment to actually install an asphalt driveway there are many things you can do to prepare the drive for paving work. The driveway without exception must have a solid base underneath to pave upon. Soft or wet spots are the most common reason for failure of the pavement itself. Cracking or alligatoring means the ground is unable to carry the weight of the vehicles driven over it. Severe wet spots will cause the pavement to fail totally and breakup into large chunks and cause the entire driveway to fail.
There are available today ground stabilization fabric materials that can be laid under stone sub base materials in wet areas to help solidify the sub base itself. The material is fairly expensive but may allow installation of a driveway where it would not be possible other wise. If placed directly on the earth below the sub base and over the wet area, once the sub base material is properly compacted the ground will support a great deal more weight without and shifting or movement.
Many masonry supply stores carry these Landscape Edging Guys It will take two people to roll out and handle the fabric as it generally comes in twelve foot wide rolls. A local excavating contractor may have some smaller rolls to sell. Give them a try as well.
Our first job is assure there are no wet spots either by installing some under drains, ditching along the edges to carry away surface water or actually replacing some of the wet earth with stone or other suitable materials. Sub base materials could be small and large stones, DOT item 4 materials, crushed gravel or bank run sand and gravel perhaps. The material needs to drain well and can be compacted with mechanical compactors.