You should read the questions carefully in first 15 mins, and decide which questions to do or not.
While reading question paper, in first 15 mins you should decide which question to write first so you should impress examiner.
Try to write short answers and on point, you can determine the number of words to be used according to marks.
Do not decorate the paper, use only 2 Pens & Pencil for diagrams. And do not panic while writing answers.