The LGV theory and hazard perception is very similar to the tests you may have done when getting your car licence. There are some different sections to cover the vehicle type however the biggest difference is there are double the number of questions so you need to know your stuff.
The best way to do this is by studying and practicing the questions over and over again. The same goes for the hazard perception which is a case of identifying the hazards and clicking at the right time.
For just £12 you can have access to an e-learning system on your phone that not only allows your to practice mock tests but also identifies topics that you need more practice on and adapts to ensure you get more of these questions.