Socialising with other dogs
Ideally start by introducing your dog to another dog of similar temperament, age and size. Begin by having both dogs on leads and bring one dog slowly toward the other so that they're nose to nose. Allow the dogs to greet each other for a few moments and then walk one of the dogs away. Following an initial positive meeting, you can then have the dogs greet each other again, this time letting the leads trail on the ground. This will enable the dogs a bit more freedom while allowing you control to walk in and easily remove one of the dogs if needed.
Once you're happy the dogs have had some pleasant initial play you can take both dogs off their leads. Put both dogs in a sit position, unclip the leads and then let both dogs go. With the leads off there will be no tangling and they can enjoy some natural play.
How to socialise a dog with humans
It's equally important to have your dog learn to greet people in a calm and controlled way. To keep your dog calm and from jumping up you'll want to start with him in a sit position. Ensure that the person greeting your puppy isn’t overly excited either. Have the person greet your dog in a nice, calm manner and give him a treat. This will help reinforce a positive connection with new people.
Top tip: When meeting new people you may want to have your dog on a lead allowing you more control if your dog gets overexcited. You can then lead him away, settle him down, and make another approach when things are calmer.
The more you can socialise your dog in a controlled way to the various things he's likely to encounter in life, the more resilient and adaptable your dog will be.