Hii

For writing a 5 marks question in board exams, I can suggest you that firstly on reading the question, make up your mind what is the answer to the question and decide 5 main points.
Start with the first point and elaborate the point with relevent example if possible and put up facts from the chapter.
Then move to second point and so on.
Make sure you divide your answer into 2-3 paragraphs so that it becomes neat and easy to read. 
Underline the important points so that it becomes attractive and the teacher focuses more on those points which you believe are important.
If the word limit is 120 words, make sure your answer has minimum 125 words and not less.
If the question is for ENGLISH Subject- these points are enough for scoring full marks remember using the facts from the chapter.
If its about science subjects like physics chemistry or biology, include examples from the chapter which are relevent. Include diagrams and figures.
Make your answer attractive. Attractive does not mean that you will sit and keep on coloring your answer. but attractive means it should be neatly written and proper spacing must be done, if a diagram is added, make sure to label it properly.

Hope this helps and feel free to revert back for any more query.
Thanks!