Re: Meeting with producer
First, do your homework. Is he the real deal? Does he have reasonable credits which you can confirm?
If so, then great, sit down with him. He will tell you what he likes about the script, he will tell you why he is awesome and can get the movie made and he may tell you what he doesn't like about the script and wants to change, i.e., he will give you notes.
If you agree with his notes, go ahead and spitball with him and let him know you agree. If you don't agree with his notes, let him know you'd have to think about those and you might have some questions. Then let it percolate for a bit and get back to him later on.
He may suggest optioning the script. You can tell him you have an attorney and you can give him the contact so that he can send any offer to your lawyer.
He might want to not do that and keep it between the two of you. Tell him fine, send it to you and cc the lawyer, and you'll get back to him.