Don't even think about fishing in front of my campsite!
On my first trip to the BWCA I was taught to avoid occupied campsites, which includes campsites which you are not sure are occupied or not.  If you are paddling down the shoreline and you see on your map that a campsite is coming up, you paddle further out into the lake.  The idea is that people have come a long ways to have a "wilderness" experience and we should allow them to have that, or at least the illusion of wilderness, and not interrupt it with our presence.  If there are others around, don't be loud, be quiet.

Many times I have had fishermen anchor directly in front of my campsite less than 30 feet from shore.  A couple of times there were only two campsites on very large lakes and the people at the other campsite paddled all the way across the lake to anchor in front of my campsite.  No other place on the entire huge lake was good enough for them to fish at. And, these people never catch any fish in front of my campsite, so it's not like it's a hot spot.  This makes me furious. If you fish in front of my campsite, I will immediately get in my canoe and paddle out to you and ask you how many fish you are catching, I will tell you that I have fished and fished right where you are fishing and I didn't catch a thing.  I will harass you until you leave.

Do not bring a guitar because the sound travels across the water and you are forcing everybody camping on the same lake with you to listen to your music.  As with fishing by my campsite, I would yell loudly across the lake to request all my favorite songs and boo the songs you pick and generally harass you.