Dear Haridas Raikwar,
Everyone of us aims for success in our chosen field in life. Know that there is no short-cut to success; you must work hard. So, there are some tips and tricks/techniques to do well in exam but finishing the complete syllabus and having understood the basics of the subject/course should be the main concern for any student.
Take the exam seriously and prepare in advance. Your time is very precious so use it wisely. Get a proper time-table/routine which really helps. Be attentive at class; make notes/key points and get them checked; revise them. Some facts to be remembered in parrot-fashion (mathematical formulas/dates and years from history/important facts in geography etc.) whereas others need proper understanding. Learn to differentiate them and work on that.
Do take care of your health. Don't forget to get your body daily vitamin and mineral requirements it needs. Have your meals properly. Cut down your intake of coffee/tea; instead have fresh fruits (they have powerful antioxidants and other nutrients; the natural sugars in them will offer you energy on your desk); get lots of fresh juice, milk, anti-oxidant-rich green tea or water and stay well hydrated. Have sound sleep.
Never panic with the exam paper on your hand. Be confident that you know the answers. After carefully going through the entire exam paper, start with the easiest questions first (and forget the order) that will boost your confidence. Don't overlook the marking scheme and devote your time to any answer according to the marks. If you're running out of time and there is absolutely no time to explain, answer in bullet points. Sometimes, we get stuck and become blank to start how to answer which is merely a waste of time. The best is to move on attempting next question and come back to the previous question after some time; often it turns out relatively easy and clear. Check your paper and revise your answers at the end. Hope these will help you. Good luck to you.