Grooming a long-haired dog requires regular brushing to prevent matting and tangling. Use a slicker brush or comb to remove knots gently, starting from the ends and working your way up. Trim any excess hair around the eyes, ears, and paws carefully. Regular bathing with a dog-specific shampoo and conditioner can also help keep their coat clean and healthy. Consider professional grooming for more intricate trimming or styling.