A. Slow down or stop
B. Close your eyes
C. Flash your headlights
D. Turn your head away
Being dazzled will be a result of either natural light or artificial light at such an angle or intensity that it blinds you so that you can't see other features in the road. This light could be shining directly at your face, or it could be reflected off buildings (particularly on windows which act like mirrors) or other vehicles (chrome work or windows).
When you are dazzled, look to the left of the road and slow down. If you can't see, you may need to stop and wait until your eyes have adjusted.
If you are being dazzled, there's a chance that the vehicle behind you is also being dazzled so avoid heavy braking or you might cause a nose-to-tail accident.
Sun strike or sun dazzle is a phenomenon that occurs when the sun sits low on the horizon directly ahead of where you are travelling. If you are short then you will find that sun visors in your car are less effective. If you're riding a motorbike you will need to have sunglasses.
Normal street lighting and lights on property are not usually bright enough to dazzle you. The main cause is other vehicles' high-beam headlights, or poorly adjusted low beam lights. If a person forgets to dip their lights then the blinding beam (along with the lack of general light around you due to it being dark) will make it hard for you to see where you are driving.
However, low-beam headlights can also dazzle if they are not adjusted. A motorbike carrying a pillion passenger or a heavy load in rear panniers will have more compression on the rear shock absorber which will lift the front up more, angling the low beam headlight higher. In a car, if it is heavily laden in the boot, or towing a trailer with a lot of weight on the towball, this can also angle the lights up.
Many modern vehicles have self-levelling headlights. Most older vehicles have a way of adjusting the angle.