Inasmuch as people have varying strengths in different areas, one of the areas where those differences are most visible is when it comes to the ability to learn and teach other people the things that one has learnt. In school, it is always distinguish those people who are able to learn easily and very quickly. In this, it is usually obvious that people usually have varying strengths when it comes to different subjects, meaning that while a person might be exceptional in mathematics, they may be barely above-par or even below average when it comes to language or other courses.
If you have a degree in a particular subject or just have a particular aptitude for it, this presents an opportunity for you to make substantial amounts of money regularly from teaching people what you know and helping them to do well in their schoolwork. Obviously, this gives a dual benefit to you, in that you are able to earn money from what you are doing, and also gain the satisfaction of helping students achieve academic success.
Generally, there will always be a steady market for any subject that you are willing to teach. This is due to the fact that in any given class, there will be people who are bad at that subject. Over time, you may come to realize the particular subjects that are particularly difficult in a particular school due to a variety of factors. It is possible for you to take multiple subjects, however, it is always a good idea for you to focus on a particular subject or category of subjects such as the physical sciences, music or any other ones in which you are exceptionally good. This will make it much easier for you to build a reputation as an authority in that particular field, as opposed to seeming unable to decide about what exactly you want to do.
One other thing that you need to decide when you are starting out as a tutor is whether you want to be a personal tutor or a group tutor. If you decide to be a personal tutor, this will mean that you will only be teaching a single student at a time, and while this will give you the benefit of being able to charge higher rates as well as more engagement with the student, it will definitely restrict the number of students you can teach and in the long run, reduce the amount of money you can earn. On the other hand, you could choose to be a group tutor and teach multiple students at a time. This would likely amount to a lot more money, but it might also act to reduce your efficiency in that you might not be able to engage with them as much.
You can get students to hire you by placing advertisements that include your contact details in school areas, and you can also decide how you want to be meeting the students, whether at the library, a park or any other location you deem best.