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If you have never groomed a dog before, you will need to learn the basics and practice.  Consider an apprenticeship. The best way to get hands-on-training, if you are not enrolled in a school program, is to apprentice with an established groomer. If you are in the United States, consider taking the National Dog Groomer’s Association of America exam. This certification program will allow you to be recognized as a “National Certified Master Groomer”. This is very attractive to see when employers look at your experience. A variety of grooming schools exist that offer certification and hands-on training.  There are dedicated dog grooming programs that are offered through larger organizations, like through the Animal Behavior College.  You can also enroll in pet grooming programs that are offered through organizations that are dedicated to pet cosmetology, like the International Society of Canine Cosmetologists.  Your local community college may offer pet grooming courses. Some salons and groomers will offer on the job training for entry-level groomers and new hires. Different dog breeds have very different coat types and grooming needs. Getting experience with a large variety of breeds is an important learning experience as you become a dog groomer.  Some breeds, especially those with longer hair, like Maltese, Spaniels, and Malamutes, require more intensive grooming.  The majority of pets that will come in to be groomed will be dogs, but you may have to groom cats and small pets like chinchillas or guinea pigs. You may or may not need to receive specific pet grooming certification or licensing to operate in your area. This is going to be unique to your location.  Some states require you to receive a license to administer flea and tick medications. Check with your state to see if this is the case. Your area may require you to receive official dog grooming licensing through a certification program. If your area does not require you to this, it may still be a good idea to go through this program as a way to build your credibility with clients.  There is no standard education requirement or formal certification requirement to be a dog groomer. Most groomers have a high school degree and have completed some sort of training, whether that is through an apprenticeship, an online program, or an in-person program. After you’ve trained to become a pet groomer, you now have options as to where you want your career to begin.  Decide whether you will operate the business as the sole groomer or if you want to run a salon with other groomers.  You could also work for a large pet store that offers grooming. You can work at a vet clinic or a doggie day care as a grooming specialist. You could offer mobile pet grooming.
Gain experience. Enroll in a dog grooming school. Practice with different breeds. Get licensed. Decide where you want to practice.