I was lucky enough to be born smart enough that I never had to really put any effort into learning. But on the downside, that means I never learned how to put effort into learning.

That said, I've noticed that the biggest difference between me and my classmates was simply the way of looking at problems.

Don't choose classes based on what you find easy or fun. Take them based on what will be useful, even if only peripherally. Knowing about some things will make it easier to do related things - for example, I took a CAD class even though I knew I was going for a CS degree.

It is not important to finish all your homework. It is important to be able to prove, at any moment, that you could complete the homework. It's better to spend that time learning the material, or related material. Do not take this as an opportunity to just be lazy and do other stuff, it is very easy to not learn anything in that case. As a self-check, do a random sampling of each homework assignment's problems (not the first ones, since they are usually the easiest - in particular aim to do either the hardest or second-hardest).

Remember that teachers are not always in it to teach you accurate information, sometimes they're in it because they love to be unquestioned. As someone who was smarter than most (if not all) of my teachers and could pick out their lies, this was a problem for me. I'm not sure what I would have done differently, but it is really important to recognize that not everything you're taught is actually true.

If you have friends that are dropping out of school, drop those friends. Any friends you have now you'll rarely talk to again after high school. And the high school social environment is very harmful. Don't get involved - you'll never see these people again for the rest of your life. Don't go to parties, and especially don't go to bed after 10 PM or so. Sleep is how the brain stores knowledge.

It is okay to have hobbies that interfere with your study time, but only if those hobbies produce something, rather than consume. Nobody cares if you can name all 151 pokemon or do the jump on Rainbow Road. They do care, if but for a moment, if you're good at basketball, or if you can do something artistic, or write computer code like I do. Having a hobby that produces something is a great way of managing procrastination.