Jot down points in your favor:
The first step is always to list down why you think you are right and should protest. These points will serve as your agendas and attract supporters for you. Make them convincing enough. This process will also help you decide for yourself whether you are right in protesting. It might even make you more passionate. Be logical and reasonable in what you demand for.
The more supporters you gain, the better chances you have to get heard and change things. If it is home and you want to protest the t.v timings, involve your siblings in it. At school, start with friends and expand the circle of followers. The points you made in step 1 are going to help you convince people about your cause. You can use word of mouth, emails, telephones, flyers and announcements before classes(or dinners at home) to get maximum audience. Arrange regular meetings and communicate frequently with supporters to be on the same page of events.
Write petitions and get signatures:
Write a document that states your opinion and get signatures of your supporters on it. This way the whole affair will get a mature look and you will no longer be ignored as some crazy up to no good teenager.
Choose a peaceful way to demonstrate:
No matter how angry and frustrated you are, you must always choose a peaceful but effective way to protest. Destructive acts will only harm your cause and may even worsen the situation by making the authorities stubborn who may be your parents, school heads or any one. You can put up posters on the school walls or notice boards. If it is home you can put them on the fridge. The most important forms of protests include walks where you carry banners and chant your demands. You can arrange a meeting with the authorities or your parents and make them listen to your point of view and why you believe they are being unfair. When you adopt the legal and constructive ways to protest, people are bound to listen and agree. Remember you should always be diplomatic and have a bargaining stance. Something is better than nothing.