What's the best way to prune a Rose of Sharon tree/shrub?

hmm.. I usually prune mine just around the top, or sides... you can cut off the smaller branches like you would prune anything else.. just cleanly chop off what you want.. but mostly only the smaller, thinner branches..

You can also root the cuttings - they will probably droop for a day or so, but all of the ones I've done have grown successfully afterwards.

I knock mine back every year about half way down on all the thin branches and it shoots up in the summer