The only thing i know is to check for dehydration. Pull up the skin on your cats back between the shoulder blades and let it drop. It should drop quickly (i.e. if it's slow or the skin stays tented then your cat is dehydrated).
You could try getting a pet fountain, as the running water often encourages your cat to drink more. Also consider adding wet food into your cats diet as this provides a lot of the moisture your cat needs.
My MIL just bought a fountain for her cats and they love it.
Anyways, besides the skin tent, you can also feel the gums, as long as they are nice and moist then hydration is good, if they are tacky, then that could mean that the kitty is a little dehydrated.
Wet food is a good source for some extra moisture.
(Cats should drink ~ 1 oz of water per pound of body weight.)
Measure the amount that you put in the water dish, then before you change (or refill) it dump the leftover water in the measuring cup and subtract the remaining amount from the initial amount.
My girl eats only dry food. I notice that she drinks more water when she has more than one water dish. I think she likes the variety, go figure.
The vet checked her yesterday and Gizmo was extremely 'well hyrdated'. Pulling up the skin on the shoulderblades is the usual test; if it stays up and takes a long time to re-settle, the cat is dehydrated.
I've always used the scruff skin test (cept I was taught to pull it up and twist it a little... if it untwists and sinks back down right away, you're good)... Oliver eats only dry food as well (although he's actually starting to show a little interest in wet food for the first time, but he'll only eat a mouthful at a time - thank God for tupperware and fridges!)... he has 3 water dishes and his skin and urination are quite regular.
i did the scruff skin test and the skin moved back quickly.
i will measure how much water they drink next. i have 3 kittens that total 16lbs. so if each kitten drinks 1oz then 2 cups of water should be drank per day, which i doubt happens, but maybe.
i am thinking about getting a fountain if my cats arn't drinking enough. i do change their water about 3 times per day.
Adding wet food really helps hydration. There's also no reason you can't hydrate their dry food to increase their water intake. Just keep in mind that you shouldn't leave wet food of any kind out for them for more than 30 minutes. This includes hydrated wet food. My cats on a raw diet rarely touch their water dishes and are very well hydrated.