My tip would be to try to understand things at school and university, if you can. It takes a lot less time and effort than trying to remember it all, and while grades open doors, in many fields knowledge without understanding doesn't take you very far after studying.
Also, the earlier you really understand things, the easier the next things are to learn. Many things seem more complicated than they are when you are first taught them, often because a teacher is crap or society says it is difficult. Ignore such thoughts and let curiousity drive you.
Probably ignore this one, because it might be seen as irresponsible, but I'd also say don't try to attend every lecture at university because they are usually a crap way of teaching and you'll just end up too tired to reflect on and understand the subject matter. Also, more importantly, the time is better spent enjoying life. I have found that lectures are only really useful when they are interactive or you are learning something interesting in a field where you already have the basic knowledge. If you want to learn the basic knowledge, you are far better with a book, the Internet, or sitting down and discussing it with someone who knows. As above, to understand is the goal, so where possible ask the questions you need to get there.
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