Chapped lips occur when moisture of lips disappears. The main cause of chapped lips is exposure to sun, wind, heat and dry air as all these conditions take the moisture from the skin.
Drink lots of water:  People who do not drink sufficient water are more prone to get dry lips.
Apply lip balm or petroleum jelly on the lips to keep them smooth
Stop wetting lips with tongue rather apply moisturizer.
Applying glycerin on the lips with a little honey to it too is quite helpful in healing the cracks of the lips and to make them soft and smooth.