Getting a part-time job is a good way of gaining work experience and earning some money at the same time.
You may not mind what you do - you may just want to earn some money and have some independence. But did you know that you'll need a work permit and that there are also some jobs that you can't do until you are 16?
It may be that you are keen to get a job to improve your chances of getting an Apprenticeship or onto a job-related course such as a child-care course at College or a medicine degree at University. If you are trying to find a job in a specific area like this you may need to consider doing un-paid work experience as a way of getting started.
The best way to approach getting any type of part-time work is to start by identifying employers who you could target and then approaching them about work-experience or part-time vacancies. Use the sections about job hunting on this site to help you get started.