This is pretty basic, but whatever.

As you may or may not know, towers do not give your heroes experience when they kill units. So when you surround a unit in your base or something, you want to make sure your tower does not get the last hit. One way to do this is hit ’stop’ on the tower to keep it from attacking when the unit you’re killing is low hp. Alternatively, you can make the tower attack your main hall or another building; instead of spamming ’s’ on your tower, you can do other stuff now.

Just make sure you don’t forget about it :P