http://stanspoint.blogspot.com/2011/08/thirsty-thursday.html
Part of the reason that you can go for hours or sometimes a whole day without drinking is that thirst is a delayed response to dehydration. As your body becomes dehydrated it takes a while (anywhere from 1/2 hour to several hours) for it to signal to the brain that it is dehydrated. Even after you become thirsty, you still have to stop what you are doing and takes time to find something to drink (which prolongs the dehydration even further).
The other problem is that even once people become thirsty, people will often drink a whole bunch of water all at once (they chug, chug, chug). If you try to drink a large amount of water all at once, your kidneys will simply flush the excess fluid by sending you straight to the bathroom (and hopefully you make it on time).
As thirst can be unreliable, it's better to drink regular amounts of fluid throughout the day (and if you are going to be working out, in the sun, etc... drinking water frequently during that period). One good way to remember to drink is to find a cool (as in one you like - like the ones I have below) water bottle and each morning simply fill up the water bottle. Then you just make sure that between each meal (or if you forget to eat at least by the end of the day) to empty the bottle (by drinking it of course). By doing this, you won't forget how much you've already had to drink each day. Do the same for your children (because they won't understand to keep track themselves. Remember: If they're thirsty, they're already dehydrated).
There are a lot of things you may forget in like (birthdays, anniversaries, to mow the lawn) but remember, Don't Forget To Hydrate.
Daily Drinker
http://www.kickstarter.com/projects/korwater/nava-a-revolutionary-filtering-water-bottle?ref=live
Athlete on the Go
http://www.kickstarter.com/projects/1708318461/simple-hydration-water-bottle-for-runners-active-i?ref=live