Establish good study habits. Don't be afraid to ask for help. Teachers are paid to teach--make them earn their paychecks by asking questions when you don't understand something, and if you need more than one question to get there, ask it! Put study before socializing. Go beyond the assignment, in other words, go the extra mile. If a subject really "grabs you", read more about it. Take notes--LOTS of notes. If you're not sure how, google "note-taking skills", and you will be directed to all kinds of sites for this vital skill. I would say that good note-taking is probably the most important skill you can learn.
The ways in which one can be effective in school are having a vision for success, setting high expectations for achievements and building leadership capability. Participating in games and other school events are also ways in which one can be effective in school.