Most building inspectors will have a pinless moisture meter on hand, this is the easiest way to determine if there is moisture on hand.
If you notice signs of water damage on the wall, such as rusty water stains, bulges, sagging walls, bloating of the walls, or mold growth, these could be signs to confirm the moisture. If these signs exist, make sure to call for a professional to come figure out the source of your moisture problem.