Another water-related myth you'll hear time and time again: "8 glasses a day"http://www.snopes.com/medical/myths/8glasses.asp
As the Snopes article states, we get at least 4 glasses worth of fluid from solid food; while tea, coffee, fruit juice and even soft drinks will make up whatever else you need. As for when you need to drink, that's easy enough: whenever you're feeling thirsty!
Someone earlier linked polyunsaturated fats and heart disease: I think they probably meant saturated fats. Saturated fats are animal fats and tend to be solid at room temperature. Unsaturated fats (vegetable oils) are slightly less unhealthy but still should be consumed in moderation. That includes Omega 3, the reputed health effects of which are well known, but it's still thought that large quantities (over 3g) can be detrimental.