Good article with multiple methods of harvesting water in different environments.
http://modernsurvivalonline.com/how-to-find-water-the-most-valuable-survival-skill/Once again, PRIOR practice is going to be a great help... You've got LESS then 3 days to get this right and you will probably not be thinking clearly and getting more confused as time without water passes.
Immediately start looking for water sources. It should be you first or second action. Shelter might be first, depending on how harsh your local environment has become...