Each state controls the law that determines what you have to say and whether you can record the call.
Here in Indiana, as long as one party agrees to the call being recorded, it's OK.
I have a $10 device on my phone that runs to a tape recorder. I'm a journalist. I use the device to record calls so I can take better notes and to ensure I quote people properly.
I don't have to tell anyone I am recording them. I generally do as a rule, because I believe it's the ethical thing to do. But it also protects me from people who are pissed at me, or those mindless phone calls at 3 a.m.
It also protects me against telemarketers. If I buy something over the phone, I record the call. I also tell them, when they tell me, that I am recording the call. I find I generally get better service.
Anytime I call anyplace I get an automated voice telling me my call may be monitored. I don't really care, I just wish I could speak to a human being. I am on Indianas no call list and I am not bothered at all by telemarketers. It's usually places I call that are monitoring me. ON the other hand, I do get automated calls from certain companies, credit card companies, etc who leave me messages. Companies don't even answer their own phones anymore. jeez.