During the first grooming session, the main idea is to familiarize puppies with the process. A pup’s initial experiences set the stage for how he responds to being groomed for the rest of puppy’s life!!!!. So it’s important to make the experience as pleasant as possible.
Groomers can get a jump on navigating the challenges of introducing a puppy to the pet grooming process by giving their owners some tips for preparing the pups for what could be a scary experience. The more socialized and used to being handled a puppy is, the better.
I always encourage pet owners to prepare their pups to be handled in ways they might not be used to. For example, they may want to regularly tickle their paws (including between their toes), ears, and tushes, which are some of the areas the groomer will be working on.
On the big day, when the puppy first arrives to be groomed, I ALWAYS start by slowly introducing myself to the little one by speaking in a soft, soothing voice, petting and cuddling the puppy and playing with them for a bit. By gaining their trust, I enable the puppy to regard grooming as a fun, enjoyable experience. Above all, PATIENCE is key. 
Bear in mind that pups may be frightened when they are first exposed to such alien devices and tools as clippers, noisy dryers, and grooming tables. The first experience must be a good experience, with lots of love and treats. This is their special place away from home. If groomer PUSH them through the experience and RESTRAINED  them, then you ruin that dog for the rest of his life.
Many puppy owners make the mistake of waiting until their pups are six months of age or older before taking them for grooming. As a general rule, puppies should be no more than 16 weeks old, as younger pups are easier to train. They also need to have had all of their shots before being groomed for the first time. The initial grooming sessions should be kept short and sweet. It takes two to three sessions for a pup to become totally acclimated to and comfortable with the grooming process. But if approached the right way, this can enable a pet groomer to establish a lifelong happy relationship with their new pooch clients, which will ensure their long-term health and happiness.

Regards Isabelle.