 
Your child will behave like the angel he is when he’s invited to a playdate if you lead him to success with one key strategy says Jenn Berman, author of The A to Z Guide to Raising Happy, Confident Kids:
 REMIND AHEAD OF TIME!
• Go over good-behavior expectations at home with your little one before embarking on a playdate (or birthday party or other outing).  Do it one more time just before delivering your child to the playdate or party, i.e. Encourage your child to play nicely, meaning, sharing, taking turns, not interrupting, not hitting, etc.
 • Talk about having nice manners, saying “Please,” and “Thank you.” Explain to your child why it would be wrong to say to a friend, “I hate that toy,” (because it will hurt the other child’s feelings.
 • Introduce your child to everyone at the playdate and be sure he knows where the bathroom.
 • Don’t deliver your child hungry to a playdate. If he has any food allergies, send him with his own snack. Also, tell your child NOT to ask for snacks or anything, but to wait to be asked. By all means, tell him NOT to go into the other Mom’s pantry!
 • If your child brings a toy to share, help him store it in one spot (and his shoes and coat) so he knows where it is and to keep it there when not in use.