Today I'm going to be giving advice on how to do well in school. I don't think there is any secret really. Those who do well are working very hard. Probably many times harder than you would ever imagine, but they just don't say it. Here are a few tips that have helped me.
1.) Don't get behind. If you don't understand something, keep working on it, even if it takes you all day until you get it. There are so many great resources, like teaching videos from Khan Academy to help you out. I think the #1 reason people don't do well in school is falling behind. Once you are behind you won't understand the next lecture as well and it just gets worse.
2.) Do all the homework questions and more. Practice. Practice. Practice. That is the secret to doing well on tests. The more homework you do, the better you will do on tests. You should even work on homework that is not assigned, but related to what you are trying to learn. Don't view homework as something you have to do, but a chance to learn the subject better.
3.) Don't miss classes. If you are sick, stay home, since you don't want to get other people sick. But you should try your best to make it to as many classes as you can, since you can miss valuable information. Getting notes from a friend is just not the same thing.
4.) Be an active learner in class. Just don't sit and hope you learn what the teacher is saying. Be actively trying to understand it and see how things relate to other things. If you are taking notes, don't just write down what is being said. Put it in your own words so you can better understand it. Later, you should go over the notes that same day and make sure you understand it all. Each day you should also briefly review past notes. When it comes time for test day, you will be almost prepared without having to do much more than review new material. I organize my notes into flash cards, so I can quickly go over them each day.
5.) Have high goals. Aim to get 100% correct on a test. Don't just skip concepts you may not feel comfortable with and hope for a passing score.
6.) Try to see the big picture in everything. Most subjects are really simple when you see the "big picture". All of math is about representing one thing for another. For example, x=5+2 is just another way of saying x=7. The same rule applies to a huge complicated equation too. You can do things to both sides of an equation and it still represents the same thing. In writing, a paragraph starts with a topic and develops it. A chapter is a collection of well written paragraphs, etc. Seeing the big picture will help you with any subject.