How do you know that Ad-Block and Tracking Block software really works?

I use Chrome 95% of the time. Among other extensions, I am using AdBlock. I’m also using a recently released module from AVG called “do-not-track”.

AdBlock seems to be effective in that I am not seeing ads, which is fine with me. My question here is whether or not the server (who is supplying the ads) is getting back information * about* me, whether the ad shows on my screen or not.

With the AVG Do-Not-Track plugin, something is working, because it lists for me all of the blocked trackers. And since i installed that, I can’t get into FaceBook Scrabble any more, since they apparently require tracking in order to play Scrabble.

But how do I know that the tracking to other sites is really turned off?