When you live in a humid area, moisture can enter your salt shaker, making your salt clump. You're left with a hard clump of salt you cannot get out of the shaker. Once this happens, there's no way to save the salt inside for consumption, but you can get it out and prevent it from happening in the future.
Unscrew the shaker's lid.
Turn the tap water on. Hot water will dissolve the salt faster.
Pour the hot water into the salt shaker. Allow it to run until it is coming out of the shaker.
Cover the shaker with your finger and shake hard. This helps the salt dissolve.
Dump the salty water out.
Repeat rinsing until all the salt is gone.