We have spent centuries involving dogs in our lives as workers, protectors and companions. They WANT to be part of our lives, and most people take on a dog to be part of their life in some way or another. Socialisation is all about preparing a dog to be bomb-proof in the life we want or need it to live. There are certain "windows of opportunity" for this. The best time to socialise a dog is up until around 18 weeks, but that's not to say there's no point in trying after that, though.

You need to expose your pup to as many varied experiences as you can find. This will build his or her stability in a really broad set of circumstances.
But there is a dark side to this. Experiences can be good…..or bad. It is ESSENTIAL that your pup has good experiences, and feels safe and secure that you've got his or her back. Pups can learn lifelong fear from a single negative experience.
Socialisation begins before you get your pup. The amount of handling a puppy has in the early days, watching its mother's attitude to life, and the age it leaves home are all factors that can make a difference.

Once you have your pup, you need to consider the vaccination protocol before you can do too much outside your yard.
Puppy PreSchool is a great start, as long as there is not too much rough-housing and free play with other pups.
Once vaccinations are complete, you might consider making a list of what to introduce:
People
Dogs
Kids (even if you don't have any)
Other animals (cats, horses, cows, sheep, chickens)
Traffic (cars, buses, trains)
The Ocean, etc,etc
(See the Resources page for some further ideas)

Don't push things. The idea is that the pup gets to observe from a distance, and approach safely from curiosity. Shoving the pup straight at something will just set you back. Patience and a positive attitude!
CAUTION: be very wary of off lead parks and dog beaches when training a new dog. Some lazy owners happily let their untrained, anti-social dogs off for easy exercise, and your pup could wind up in a sticky situation very quickly.