What did Charlie do at Craig’s house? Was he right in doing this?

I'm not sure when exactly Charlie goes to Craig's house. Are you referring to when Charlie tries LSD? If it is, Charlie quickly regrets his decision.

Charlie was dared to kiss the prettiest girl in the room. He kissed Sam instead of his girlfriend, Mary. He wasn't right in doing it. He should of told Mary that he didn't want to be with her anymore instead of kissing another girl in front of her.