The first step is to make sure you are capable and active enough to be a member of your neighborhood watch. Since the work may expect you to make rounds of the neighborhood, it is imperative that you are physically fit for the task.
Check your availability. There may be times when you would be requested to keep an eye on the neighborhood at night. This might hinder your professional, personal or social life, and so you will have to be good at managing your time.
If you think you are fit to be on the neighborhood watch, then contact your local police station. The main office of Metropolitan Police London is;
Metropolitan Police London
You can also visit the Neighborhood Watch’s website that has information to help you get started if you want to initiate your own neighborhood watch team.