I usually don't answer if it's not someone I know, but when I do, I never say "hello" or answer "yes" to anything. I'll answer with "accounting office, Judy speaking" because answering "hello" will tell the computer dialer to route the call to an available person or trigger the computer to start responding. Even if answering "hello" sometimes there are no agents available on the other end to speak to us and so in those cases the computer will automatically disconnect from us. Also, I never say "yes" to any questions because that can be recorded and manipulated as acceptance of something we didn't intend or in answer to a question we were never asked.
I have noticed a decrease in calls that, for my office, typically are related to credit card processing, health insurance, Medicare Advantage or Medigap, and sometimes life insurance.
I don't get them on my cell phone that is personal. I have AT&T's security with it set up to route any callers not on my contact list directly to VM without it even ringing. The call log lists those as flagged from potential scammer or telemarketers. If it's a real call, that person does have the ability to leave me a message. It works well.
On my old phone I used to get calls in Chinese that were out of NY and turned out to be a scare scam directed at Chinese immigrants to get them to pay a fee so that they were not in danger of deportment. The scammers knew that only Chinese speaking people would understand and possibly fall for it with the rest of us simply ignoring it by hanging up. Those calls have finally stopped for me.