At first see the person when your child is not with you. Kids attach very easily, and will feel hurt if things don't work out. Make sure that she doesn't feel left out or that a stranger is more important to you than her.
After you have spent some time building a relationship and you feel sure that this person is worthy of you and your child's time, then introduce your child gradually to the person. Go have lunch at the park. Go bowling together. Go to a movie. Allow opportunities for the relationship to develop naturally with your child.
Do not rush into anything (especially sex) - take things slow and let her adapt to the changes in your life gradually and comfortably. Be mindful of her feelings.
