I'll add this: the colour of one's urine may usually be an indication of dehydration. Although the colour of urine may be effected by a number of factors, if you know you havent been drinking much and you piss dark orange - I suggest you quickly skull a glass of water. This may not clear your piss up straight away, but you'll know that at least it can't be that bad.
A general rule is as stated above, drinking when thirsty. 200ml per hour and twice as much if more active, but NOT x10 much if active.
The colour of your urine is likelly to still be darker than normal.
If you are drinking a lot of beer, the colour of your urine may remain clear as beer contains water, but be also aware that once that water is evacuated, alcohol will dehydrate your body and that's when you must be particularly careful if on E.
I must also say that drinking water is mostly mentioned when people discuss E, but other amphetamines may also have a dehydrating effect. It is also very easy to forget to drink when on meth because you are too busy doing whatever you are doing, yapping away, fixing your car, stealing a TV (j/k).