Get to know everyone. As you meet people, so shall your child. Go to the park and hang out after school where other parents are. Talk to people and allow your child time to play with the other kids. If you live in an area where you can walk to school, then by all means walk to school.
Chances are other parents are walking their children to school too.
Make yourself visible to the others. Attend the school functions with your child. Some schools have ice cream socials and carnivals. Take your child to these functions. Remember that when a child is invited over to another child's house, that invitation must be approved by the parent.