Avoiding a head-on crash

It is always better to hit a stationary object than an object coming towards you at an equivalent speed to you. If you anticipate this scenario early enough then you should (with a modern car that has antilock brakes and other electronic aids) be able to apply full braking power while steering where you want to go. 

Try not to get 'target fixation' - this is where you look at the place that you don't want to go, but end up steering into it. Look where you want to go and you are more likely to go in that direction.

You will get the most braking power by remaining on the tarmac for as long as you can rather than driving on the verge where grass or gravel will have much less friction.

You should never swerve to the other side of the road as there might be other traffic coming towards you, and the other driver may regain control and move back to the correct side of the road. 

Don't flash your lights and sound your horn at the expense of controlling your vehicle. 

If you do have to drive off the road you will have to make a quick decision, especially if you are on the edge of a steep drop. And what might look like a nice soft exit (e.g. a ditch) could have a hidden culvert. Small saplings, bushes and shrubs will slow you down more gently than larger trees which will simply stay standing while your vehicle wraps itself around them.

If you are going to run into something that will cause the airbags to go off, taking your hands off the steering wheel at the last minute will help prevent broken wrists and powder burns on your arms. If your arms are crossed when the airbag goes off, the airbag will hit your forearms while you are gripping the steering wheel. This can easily break your wrist. Your arm will be flung backwards into your face which can break your nose and knock out teeth, as well as break your forearm.