I don't want anyone know what videos I’m watching/liking/commenting or any of my activity from YouTube to show on my Google+ page or stream.
I found a few settings on the privacy page:
But I can't find any settings for comments.
Update: You don't have to do anything.
The comments you make on YouTube will now appear only on YouTube, not also on Google+
The only YouTube activity that gets posted to Google+ is comments. To stop that from happening simply uncheck "Also share to Google+" when commenting.