I use this service with my digital phone, it takes care of a lot of spam:
http://www.cnbc.com/2014/01/07/free-service-p ... -robocalls.html, I believe it would work with vonage, fios phones, etc..
If I get a call on my cell and don't recognize the number I'll let it go to vm, if they don't leave a vm, I'll block it. My vm message explicitly says to leave a message, if you don't, I can't follow up. Not going to invest time to try to uncover your id, expecially when there are also ringback scams going on.
DO not call lists can be ineffective because some spammers go thru automatic dialing machines that dial 212 555 1212, then 1213, then 1214, etc., for example, and you are also providing your number to them via the list.
If I get an unknown call and answer, I'll ask who is calling, if they are selling something, I'll be "not interested, thank you", hang up and move on. If it is someone I know their number should already be in my contacts. Keep it short, keep it civil, don't engage if not interested. Thanks and good bye. :)