The cure: Drink a glass of water every hour throughout the day to stay hydrated. Ten minutes before your walk, drink a glass of water.
During your walk drink a cup or more of water every 20 minutes.
After you finish, drink a glass or two of water.
Avoid caffeinated beverages before your walk, they cause you to lose fluid, making you thirstier as well as making you take inconvenient stops along the way.
On walks over 2 hours, use an electrolyte-replacement sports drink and drink when thirsty.
On long distance walks, drink when thirsty and be sure to replenish salt with a sports drink rather than drinking only water.