Early Puppy Socialization
There is no substitute for advice from a conscientious breeder in the first instance, followed by classes with a reputable training school or club which may operate 'puppy socialisation' classes or 'puppy kindergartens' in your area.
These are popular and an excellent way of not only introducing your puppy to others of a similar age, but also to accustom your puppy to outings and the social environment in which we live.
I do not believe de-sexing has any effect on ease of trainability of a puppy and de-sexing is no substitute for responsible dog ownership. The question of de-sexing is further elaborated upon here.