Question: I've run a number of races, and there are almost always a number of water stations. I don't usually stop for water on the short races, but I'm not sure how long of a race I should do that for - when should I start drinking water? How much and often should I drink it?

Answer: 
Ideally, you'd have a little straw follow you around and you could have a constant drip of hydration. Take a cup at every water station, and take a few sips. Depending on how far apart they are, you'll want to drink more or less, aiming for an ounce of water every 4 minutes since your last station. This isn't an exact calculation, but it's a good place to start from.

This is going to leave you with leftover water almost every time. I personally would use the remaining water to cool off and keep yourself alert with a good face splash. Unless it's gatorade, then it probably wouldn't feel so good on your face :)
It's really much simpler than this. The marathon doctors have been recommending the following for a few years now, with the risk of hyponatremia in mind:

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> If you're thirsty, drink.
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Citations:

* *Runner's World* magazine, 2005: ["How much should you drink during a marathon?"](http://www.runnersworld.com/drinks-hydration/how-much-should-you-drink-during-marathon) (references, in particular, Tim Noakes, author of the widely-respected *Lore of Running* and author of the IMMDA statement below)
* Georgetown University Medical Center, 2007: ["Runners: Let thirst be your guide"](http://explore.georgetown.edu/news/?ID=25347)
* British Journal of Sports Medicine, 2013: ["Current hydration guidelines are erroneous: dehydration does not impair exercise performance in the heat"](http://bjsm.bmj.com/content/early/2013/09/20/bjsports-2013-092417.abstract)

Additionally, [this 2001 statement](http://www.usatf.org/groups/Coaches/library/2007/hydration/IMMDAAdvisoryStatement.pdf) from the International Marathon Medical Directors Association (IMMDA), which concludes:

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> "Accordingly perhaps the wisest advice that can be provided to athletes in marathon races is that they should drink *ad libitum* and aim for ingestion rates that never exceed about 800 ml per hour."
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