We have always worked on the top dog school of thought...we love Lulu but we are the bosses. She always waits for us to walk through a door before her etc. Recently, when playing tug the it game was going on too long for me and, of course, I must always win so I tried a new tactic. I put my mouth near hers and made to bite the tug, Lulu let go immediately. It's repeatable and I use it most times to end the game now.
All these years we never had a Boxer - until now! We didn't know what we were missing...now we have Lulu :)