All parents want their children to succeed socially, but are there steps that we, as parents, can take that will lay the foundation for social success in preschool, grade school, and down the road? Fortunately, the answer is a resounding "yes," and the good news is that it isn't difficult to do. 
First, lead by example, both through your interactions with others and through pretend play with your child. Children are sponges – they imitate what they see and hear. If you say "please" and "thank you," if you wait your turn patiently when in line, if you model the social behaviors you want to see, your child will imitate you. You can create the scenes you want to model through pretend play as you pretend to be mom and baby, two friends, student and teacher. Dolls and puppets can be a terrific addition to pretend play and sometimes add just enough distance to the interaction to make the "lessons" sink in.
Second, play games with your child, and set up organized play time. It is important for kids to experience following a set of rules or expectations, taking turns, winning, and (perhaps more importantly) losing. Games help children experience how to lose, and playing games with you gives them the support they need to still be willing to try again.
Third, help children learn the vocabulary they need to express what they want and need. Sometimes children act out or behave inappropriately in social situations because they are lacking the communication skills to explain what they want or how they are feeling. Teaching children to label feelings or emotions they are experiencing or you are experiencing can be as simple as stating, "You feel frustrated that you can't have the ball right now," or "Mommy is sad that Daddy has to go on a trip today." Talk through situations that bother them and offer solutions rather than just always fixing the problem. Likewise, giving them the vocabulary to ask for what they want rather than just giving them what they want when they whine , cry, act out, etc. lays the groundwork for appropriate social communication.
Fourth, it is important to offer opportunities for children to participate in extracurricular activities that require them to work with other kids in their age group. For example, classes at The Little Gym offer group activities each week that require children in the same age range to work together, providing lots of opportunities for social interaction, sharing, taking turns, teamwork, and more. When kids are younger, doing mommy and me type activities are fantastic first experiences to social settings; but as kids get older you want to look for more independent activities where they separate from their parent and learn to take direction from another adult figure or instructor. One example is a camp program or a weekly class such as those offered by The Little Gym.
Finally, take time for social activities consistently, throughout the year. Families lives are extremely hectic with parents trying to juggle numerous roles and responsibilities, and sometimes adding in a regular activity can seem like one more burden. But seeking out social growth activities that are specific to a child's age is fundamental to their growth and their future success in life.
(The Little Gym is the one source that covers all aspects of helping a child develop socially, as well as physically, emotionally, and even intellectually. Our age-appropriate programs hit the mark on each of the five tips listed here, as well as many others.)