I don't know about your high school experience, but mine didn't include how to learn proper time management and study skills. The following list is based on scientific research and studies that have proven to be effective study methods:
Actively attend your classes.
Paying full attention to what your professor is teaching, and using audio and visual learning, can encode into your brain the importance of the content, and therefore will help you to better remember it. This is called the multi-sensory approach.
Rehearsal.
Information in your brain can quickly disappear if it is not being actively used. Rehearsal, reviewing the information you obtained in class, is the first of many techniques students can use to hold the information in their brains.
Elaboration.
Whenever you learn something new, you change the neural networks in your brain. Elaboration, when you attach new meaning to something, allows you to start with neural connections that already exist and then modify and add neural connections to incorporate new information.
Chunking.
One of the most effective memory strategies, chunking is when you organize the information into smaller, manageable units. Chapters in a textbook, creating outlines, and headings are all examples of chunking.
Increase your reading comprehension.
More often than not, reading a textbook can be daunting. This is why researchers recommend first finding background information on what you are reading. This can be done by finding chapter related videos, reading the chapter summary before reading the chapter, and skimming the table of contents outline.
The 3R method.
One simple, yet effective reading strategy is the 3R method:
1. Read the material.
2. Recite the material (close the book and say what you remember or write it down).
3. Review or read the material again (add to your notes, fill in missing content and/or write key concepts in the text).
SQ3R method.
1. Survey. This means to simply preview the chapter.
2. Question. Create questions about the content, or answer the questions that the text may give you.
3. Read.
4. Recite.
5. Review.
Highlighting.
Researchers have found that students comprehend what they read at higher levels when important text is highlighted. Although, many students have difficulty in differentiating what is important and what is not, it is a skill that must be acquired overtime. Ineffective highlighting is worse than not highlighting at all.
Note-taking.
Taking good notes during class will help you remember important content, however, it is not the act of note-taking that helps you remember but rather how you use these notes after class. Note-taking shouldn't be an in-class activity only, it is important to take good notes after lectures and review both the in-class notes and after-class notes. Taking good notes may be enhanced with apps such as Evernote and Google Notes.