Depends how strange they are, usually I ask them to skype with me on video so I can see for real how strange they look. Then from there, if they appear to be normal, I will try to use a service like escrow where they have to confirm with transferring the domain first but don't think they support facebook. I would ask him to send some of the money upfront then proceed with giving him the facebook details, again depending on how strange they looked from the skype chat. Good luck bro.