Some simple tips that will help you ace Anna University exams are:
Most subjects require you to write the crust or key points only. Teachers don't prefer lengthy answers unless it is for theoretical papers like Environmental Engineering.
Unfortunately at Anna University presentation matters more than what you have written. So make sure you use different color inks and make your answer sheet look presentable.
Use a different color pen usually black for key points of sub-headings.
Supporting your theoretical answers with a well-labeled diagram will surely get you extra points.
For the numerical part, pay special attention to measurements and units as they check this part with extra caution.
Write your answers in neat handwriting as the examiners don't want to spend more than 3-4 minutes per paper checking.
Lastly if you want to increase your chances of clearing the paper, fill out the entire booklet.
All these tips combined with your own efforts will bear you good results.