Firstly, you will need to decide what part of law you are wanting to work within. There are many different ways you can work in the law industry. For example, becoming a lawyer, a solicitor or enforcing the law with the police.
Once you have decided which area you are focusing upon working within, you will need to look into what your next steps are. For most law careers you will need a degree studying law. This means heading off to university to study.
Whilst you are studying try to maintain a good relationship with any work experience you complete. This can help you in your later career with finding your first full time employment. Some companies may even offer you a job role whilst on your work experience for once you complete your degree.
However, if you are more wanting to enforce the law, you can gain a job for your local police force as a volunteer. Or even go to University to study policing and gain a deeper insight into this path.