Bit of tongue in cheek thread but one that may save you having a fall. Whilst we all look forwards while riding, there are times when you need to look back. I'll not argue what these are as there can be a myriad of reasons, some important, some trivial. The point is, if you don't know how to turn around and hold your line, you can swerve and fall or bring others around you down.
If you keep both hands on the bars and turn around to glance backwards, your shoulder rotation turns the bars and you swerve. You can't help it.
A simple practice shown to me was to place your hand behind your back on the side you are turning, then glance back. You create balance and don't swerve. Takes a bit of practice but works fine.
One of the best accessories I've bought for my commute bike is a bar end mirror. Its easily adjustable and saves me having to turn quite so often. Even with the mirror I still turn back to confirm there is no one when pulling out or turning.