One of the most common questions I'm asked regarding the hazard perception part of the theory test is 'how many times should I be clicking?' or 'do I click when I first see the hazard or when the hazard develops?'. It is true that it's possible to click too early. Just as it is possible to click too many times in which case you will be penalized and given 0 points for that clip. There's a really good website dealing with everything you could possibly need to know about hazard perception (click here).
This post was prompted by an experience that one of my pupils had a few weeks back. He failed the hazard perception part for clicking on EVERYTHING he perceived as a hazard which meant he was clicking every second or so. It really comes down to what is a hazard? The list below contains the 13 hazard groups that you should be looking out for:
1) Zebra crossings & traffic controllers
2) Pedestrians: Children and young adults
3) Pedestrians: Elderly and infirm
4) Pedestrians: Adults
5) Cyclists & motorcyclists
6) Horse riders & other animals
7) Vehicles: Moving off or pulling up
8) Vehicles: Meeting
9) Vehicles: Emerging
10) Vehicles: Turning left or right
11) Vehicles: Reversing & U-turns
12) Vehicles: Larger vehicles
13) Vehicles: Flashing lights
Without knowing exactly what you should be clicking for you can't possibly get through it without a bit of luck. Another factor is to make sure you're prepared. Do plenty of mock tests to ensure you're achieving over the pass mark consistently. Once you've done that go for your test and you should have no problem getting through the hazard perception!