It's important to keep a dog's nails trimmed but it's really hard to do it right if your dog has black nails, like Gracie does.
On dog's with white nails it's easy to see "the quick;" the soft, interior tissue of the nail that bleeds and hurts like holy heck if you cut it.
Think how much it hurts if you cut your own nails too short. If you have a lot of trouble cutting your dog's nails without hurting him (or her) it's best to let the vet or a dog groomer do it.
I cut Gracie's nails myself. I take my time and try to be super careful. I cut a nail too short only once; the first year I adopted Gracie, when I was new at nail-cutting. She yelped and it bled and the styptic powder I had on hand didn't help at all. I tried using a styptic pencil but that seemed to hurt her.
Gracie never was comfortable getting her nails cut, even before I accidentally cut that one nail too short. To make nail trimming easier on her I give Gracie a small biscuit treat before I start and after each cut. To avoid overly stressing her, I try to cut a maximum of three nails at one time. If more need clipping, I leave them for another day. I make sure the room is brightly lit so I can see her nails clearly and spot "the quick" under each nail.
I find the clippers shown above work best on Gracie's thick nails. In the past I tried a different kind of nail clipper; the kind that has a sort of hole-opening into which you position each nail before cutting it. I think that type is called a guillotine style clipper. It did not work well for Gracie, as it crushed and split her nails. The clipper shown above works much better. The brand is Millers Forge and the case is marked, "Italy."