Ah this poor soul, hanging upside down with a permanent headache. But I have always felt that while this is seen by many a stagnant and perhaps unmoving card, it is quite the contrary. I feel that this is a slow moving card yes, but one that calls for reflection rather than action.
Take The Fool for example. He is not afraid of stepping off that cliff, no matter in which way he lands.
Now think that this could be The Fool that has landed on his head. Ouch. May be next time he needs to think before he jumps. And so he swings to and fro there as the Hanged Man.
Mostly his face (at least in Rider Waite style decks) is depicted as serene, he is ok with it and with stilling himself a bit. But he also knows that eventually he is going to have to make the decision to move forward.
I tend to disagree with some of the views that see him a bit as a victim, perhaps he consciously chooses to still himself because he knows that this is no time for rushing, he knows that this situation calls for reflection.
He is looking at everything upside down, he is willing to see a different perspective or to try and take a different approach.
The Hanged Man is about letting go of the need to act impulsively. Because in fact what is after this card is Death, the changes are starting to occur, and he is ready to set them in motion.
In readings (and of course depending on the surrounding cards), this could ask you to take a different approach, take a step back and reassess a situation. You may be are going to need to examine all angles before making a decision.
But know that, eventually, you are going to have to come off that tree.