SOCIAL DIARY
First off, unfortunately learning how to learn isn't usually taught, nor is reading (beyond elementary school) taught, and we as humans have relatively poor feedback mechanisms to tell you how well we learn, so you don't know what you're doing. I don't know. (see Dunning-Kruger effect) We think we have learned something well, but we are often wrong.
However, my first recommendation is Barbara Oakley's Mind for Numbers is an excellent introduction to the subject. It is aimed at STEM fields in college, but is very useful in other disciplines and will be useful for all academic subjects in high school. You should also check out Barbara Oakley's course on Coursera, which is excellent too.
It's still very good, but a cut below that is How We Learn from Carey. 'Paste' is pretty good too.
For non-academic courses, I recommend Waitzkin's The Art of Learning and Daniel Coyle's Little Talent Book. (Waitzkin was both a chess master and a martial arts champion.)
I also recommend reading The 5 Elements of Effective Thinking by Burger and Starbird, two math professors who want to help their students learn better but generalize their concepts to all fields. It's more about incorporating and using new knowledge, which is the next step after learning, but there is a loop here, so the better you think, the better you can learn!
Also, check out Scott Young's site: http://www.scothyoung.com/blog/ He did MIT's CS four-year curriculum in 1 year on his own. (He did this with self-study materials from MIT's open course materials. Note that he's a smart guy, but not 4 times as smart as the average MIT student. He's not a child prodigy or Einstein.) He has some very good material. He mostly makes a living off of accelerated learning e-books, but the blog alone has valuable tips. And I bought some of his ebooks.
I suggest you read this blog post on BigThink: is a tactical view of learning academic subjects. What tactics are proven to work in academic settings, highlighting, reminders, etc. into research on it. (Spoiler alert, underlining doesn't work.)
That's a lot of information, but the last suggestions are not the least, I would actually cover the suggestions in the following order:
1) Start with the Oakley book. If you have the time, take the Coursera course.
2) Read Scott Young's blog for various tips
3) Read the Think Big article
4) Then read The 5 Elements of Effective Thinking.
5) Get a good book on speed reading, I like 'Breakthrough' but there are others.
6) Happy Learning and good luck!
I don't have any suggestions for language acquisition. Scott has some information on this. Like the error page in the Learning to Learn Course, I guess.