Talk to the CA as though you are speaking directly to the person you called. The CA will relay your conversation word for word. This lets the CA know that you are ready for the TTY user's reply. If the person you are calling voices for themselves, you will hear their voice over the phone. If your party does not voice for themselves, the CA will voice the relay conversation to you.
Confidentiality is the law.
The CA is required to keep all conversations private. If you would like to make another call, don't hang up. The CA will remain on the line, ready to assist you, the moment your prior conversation ends. Keep in mind that when relaying your call, the CAs will type everything you say and anything that is heard. CAs are trained and instructed in conveying the full content, context, and intent of the relay conversation they translate.