Don't talk about your invention to anyone without a written confidentiality agreement.  Exception for attorneys.  Attorneys have a legal responsibility to keep a client or potential client's confidential information confidential.  Thus, at attorney that takes your case or considers taking your case should not need to sign a confidentiality agreement.   All others should sign a written confidentiality agreement, but do not blindly trust a confidentiality agreement that is provided by the person receiving your confidential information.  Chances are that their version of a non-disclosure agreement is drafted to create large loopholes allowing them to steal your invention.