Many students sit in class, write everything down, and still feel like they understood nothing. The problem is not effort. It is method. Effective note-taking is a skill, and once you learn it, studying after class becomes much faster.
The first rule is to not write everything. Your goal in class is not to create a transcript. It is to capture the key ideas. Listen first, understand the point being made, and then write a short version in your own words. This forces your brain to process the information instead of just copying it.
Try the Cornell Method. Divide your page into two columns. The left column (about one-third of the page) is for keywords and questions. The right column (two-thirds) is where you write your main notes during class. At the bottom, leave a few lines for a summary you write after class. This structure forces you to review and organise your notes the same day.
Use abbreviations and symbols to write faster. Arrows for cause and effect, circles around key terms, asterisks for important points. Create your own shorthand and be consistent.
Do not try to decorate your notes during class. Highlighting and colour-coding is for after class, during review. In class, focus only on capturing the ideas.
After class, within the same day if possible, go back through your notes. Fill in gaps, correct anything unclear while the lecture is still fresh in your memory, and add a two-to-three line summary at the bottom of each page. This single habit of same-day review dramatically reduces the time you need to study before exams.
If your teacher writes something on the board or repeats a point, that is almost always important. Mark it clearly.
The best notes are not the most detailed. They are the ones you can actually use when you sit down to revise.