Techniques for minimising injury when falling or crashing?
In my experience dealing with crashes and bounces is like a lot of other aspects of, especially urban, cycling in that anticipation and prediction are the key attributes to getting away with less damage. 

After all, if you don't crash, you won't damage yourself (whether you're lidded or not). It's a variant on Gary Player's infamous quote, "The more I practice, the luckier I get" - the more you think about what could happen, rather than just letting the world happen to you, you'll be better at predicting dangers and avoiding them: speed into corners, visibility around bends, road surfaces, car doors, cars appearing at junctions, and so on.  

Learn to look a little further ahead - that red light 50 metres in front? React to it when you're 100 metres away (and more importantly, consider what others might do). My last crash was when I cycled into the back of a delivery van while looking over my shoulder to see if it was clear to move to the outside of the lane - while I was looking round, the van was slowing for some traffic lights I hadn't considered, so I piled into the back of him unawares. 

I know that this isn't a "what to do when you crash", but I think that there is more to crash preparation as a part urban cycling than how to fall. Cycling has a mostly undeserved reputation as being a dangerous pastime. Most accidents I hear about (definitely the handful I've had in the last few years) have been utterly avoidable and not actually that accidental.