I find that it becomes really time consuming and difficult to weed through all the calls that come in. For us, 3rd Party sites like AutoTrader, Cars, KBB, etc. are fairly easy because the vast majority of those calls are sales calls (the other 10% are wholesale, etc.).
The most difficult calls to weed through, imo, are the website calls and calls from local listings (google, yahoo, yelp etc.). We'll sometimes have someone call the sales # from our website and ask for parts or service, or call the service # asking about a vehicle. Then the listing sites are all over the board from hours & directions to vendors to service/parts to someone who drove past and looked us up on their phone.
I don't see how you can possibly listen to 100% of these calls, unless that's 80% of your day, without some kind of help from an outside company. We have to cherry pick which ones we listen to, and that's most of our 3rd party site calls and a couple website calls.