Im realizing that I've actually been chronically dehydrated for a good portion of my adult life and I'm looking to change that. I just don't enjoy drinking water (as silly as that may sound).
Tap water? If so, try filtered water, get a good, credible filter and filter the water. Depending on where you live there's a fair amount of materials in the water that make it unpleasant.
Try adding more water to dishes you eat, have soup and put in a couple ice cubes and drink all the broth.
There's various ways to flavour water to make it more enjoyable. Common ones are listed by Witchfire, but there's also commercial products that may help. Just try to avoid the ones with caffeine in them.
Really, you have to probably train yourself to enjoy water. Have a piece of chocolate or something with water. Associate it with positive acts. Pavlov yourself.