Site preparation is key to the long term health and vitality of the palm. Apart from the odd exception (Majestic Palms) most palms do not survive in boggy and constantly damp soil. If planting the palm into hard clay where there is inadequate drainage you will need to compensate for this as it can breed root rot and other fungus related diseases.
Digging a trench from the bottom of the hole that palm is being planted into is a simple way of allowing water to run off. This trench can be filled with stones, scoria or coil drain.
If this is not a viable option then you can also plant the palm half above ground in a raised bed or planter box. A slight half mound, will also allow the palms roots to grow above the water level.
For many years it was suggested that when planting into poor soil you back fill the hole with an organic compound, such as compost, peat or planter mix. This however can cause problems, if the planting hole is filled with material that is much better than the soil around it, palms roots may never penetrate beyond this rich soil. The ideal situation is to have the entire planting area rich in organic matter.
It is much more important that you apply a heavy mulch around the trunk, using wood chips, bark, lawn clippings or other similar material. As it decomposes it enriches the soil while also reducing the weed competition and water consumption. The palms fibrous roots will then grow into the mulch. Be sure to replace the mulch as it decomposes.