one guy replied to me already, he said i must pay him first though, then he'll transfer
and this in public place
What do you mean by you should pay it first ? if you are doing cash trade then ask any third party to keep the cash and just wait until he releases the coins.If the money is important to you then go with a Cop.
he could just run though!
It depends on the profile on localbitcoin you are trading with,paste the link to his id or any of his page.