While teaching one of my students yesterday we came across an example which was simple, yet nice. You can apply a “Dembo-rule” – “I would like…” from my first middlegame book to find it quickly! If something looks interesting in the position, always look for what you would like to do and try to make it work! 🙂
It is Black to move.
1…Rf3
If 2. Qxf3, Qd4 is mate.