Excuse me sir, but I found these in my biscuits.

I start when they're kittens. They're easier to manage if they tantrum at that size, and options for gently restraining them are more varied. Once they get used to the feeling it's routine for them, even if it's not their favorite thing. My oldest cat took the longest to get comfortable with it. I had to wrap her in a towel, pulling out one foot at a time for almost two years. Now she'll sit in my lap like a baby and let me trim her nails. That's my preferred way of doing it, but it requires training that can take a lot of patience.

Nail trimming is not something I have to do very often, because the most important thing in cat claw maintenance is providing them with plentiful and diverse scratching options. Different cats like different surfaces. Giving them a variety of choices keeps them away from things you don't want them scratching on. It also helps them manage their own nails, which most cats are very good at. Two of my cats are so meticulous about their claw condition that they'll pluck their own nail sheaths off when they're too long for their liking. Cats are generally hygienic and good with grooming, so if you provide your cat with the opportunity to maintain their nails through grooming and scratching opportunities, you may find you rarely have to trim your cat's nails at all.

I have three cats. They have carpet, sisal rope, and corrugated cardboard options in various forms. Some scratching spots are vertical, some horizontal, some perchable, and some loungable. The most important thing is to figure out what your cat likes and follow their lead. If you have a multiple cat household this can get expensive and crowded. It's too important for the cats not to do it, though.

Trimming an adult cat's nails when they're not used to it can be difficult. The towel method still works, but if your cat gets especially fractious they could seriously hurt you. If that's the case, visit your veterinarian for a nail trim, and if they're a quality establishment they'd be happy to try to show you how to cut your cat's nails yourself.

Every animal is different, so we have to deal with these things to the best of our ability in managing them. Nail trimming is important, and there is nothing wrong with asking for help from your vet if you find you can't manage your pet's nails yourself. Getting nail trims done at the vet isn't cheap, but if that's your only option then use it.

Side note to this novel I just wrote, OP asked a question about cats, but referenced having a dog. There's a growing trend of people making scratching boards for their dogs out of lumber and sandpaper. They encourage their dogs to dig and scratch at the board. As easy as I have it with trimming my cats' nails, I admittedly suck at trimming my German Shepherd and mastiff's nails. I take them to work and I let the professionals handle it. I haven't tried the board method yet, but I intend to.

It was a process, but we pay our cat in treats for every nail we cut. She's participating semi willingly now.

put them in a burrito