Ask the shelter what they’ve been feeding them. Start off feeding them the same thing. If you want to change their food, do it gradually- mix a little of the new food into the old food, and gradually up the amount of new food. If you change their food abruptly, it can lead to digestive issues like vomiting or diarrhea. These are usually temporary, but that doesn’t mean they’re not unpleasant while they’re happening. As a cat owner, I’d rather not deal with feline diarrhea and vomit. They don’t try to make it to the litter box when they feel it coming.
If you don’t want the cats to bug you in the morning, the secret is to not feed them immediately after you get up. Feed them in the evening, if you can. If you need to feed them in the morning, at least don’t feed them until you’ve gone through some of your morning routine (maybe after you take a shower).
Some cats can free-feed (ie, you leave a bowl of dry food out and they eat from it when they feel like it) and not get overweight, some can’t.
Once you’ve found a litter box and litter that the cats will use, stick with it. Don’t just buy whatever’s on sale this week. Cats are not big fans of change (except the kind they can bat off the dresser). They tend to express their unhappiness with their litter box arrangements by going elsewhere.
Check the amount of… er, output that you’re seeing in the litter box every week. If you’re suddenly seeing a lot less than usual, it means one of two things. Either the cats are producing less (which means a trip to the vet is probably in order), or they’re going somewhere else. You should try to find out where they are going, if it’s not in their litter box, since pet messes get harder to clean up the longer they sit.
Don’t leave string or thread around where the cats can get it. If they swallow it, it can literally saw through their intestines. This can result in a huge (thousands of dollars) vet bill, a dead cat, or both. Be especially careful with butcher’s twine that might be flavored with something tasty.
The rule in Casa Neville regarding lighted candles: If a candle is lit, an adult must be in the room with it, and must have it in their line of sight, at all times. Unattended lighted candles in a house where there are cats is just asking for trouble, and potentially very bad trouble (fire generally qualifies as “very bad trouble” in my book).
Onions, garlic, chocolate, grapes and raisins, and some other human foods are toxic to cats. If you’re going to give your cat people food, make sure it’s safe for them first. They don’t know what’s safe and what’s not. They might beg for or eat something that isn’t safe.
There are a lot of houseplants and cut flowers that are toxic to cats. Here’s a list from the ASPCA. I’d recommend not having any plants that are toxic to cats in the house. Give them away or plant them outside. This is crucial while they are kittens. Lilies are a notable example. If you’ve got any Easter lilies, they need to go before the cats show up.
Close your toilet lids. A kitten can drown in a toilet, and it’s kind of gross if adult cats drink from a toilet (at least I think so- my cats disagree). It’s downright dangerous if you use those toilet bowl cleaners that sit in the tank (2000 Flushes and similar). Stop using those if you use them. Even if you try to keep the toilet lids down, eventually someone will forget and leave it up, and you don’t want your cats to get poisoned if that does happen.