Handle them every day. Handle their paws, their ears, their tail, their faces. Get them used to being touched and handled, so it won't come as a shock when the groomer does it.
Brush them every day.
If your dog needs to have their face trimmed - get them used to having their face handled, put a teaspoon near their eyes, and give them a reward.
Get your puppy used to the sound of the hairdryer.
Remember to make it a fun and pleasant experience - rewarding with love and treats.
Stop if your puppy is not happy.