I give this advice to all the students I teach.  I found from marking ISA's and Coursework that these are the most common mistakes that pupils make and is why they do not achieve there target grade or higher.

1. Read questions carefully and highlight key points to ensure you have understood the real meaning of the question.
2. Use scientific language (keywords) in explanations.  Without scientific language you will only achieve low marks.
3. Think your answer through before you write it down.
4. Explain any process in steps, use bullet points (1 bullet point per mark).
5. Don’t repeat yourself - using different words to say the same thing over and over just wastes time.
6. When using equations always show your workings.
7. When revising never ever think you will remember something by just reading it.  Read it and then summarise in your own words without looking, ask someone to test you.  If you are stuck always ask the teacher for help.

Follow these tips and you should find that your grades improve.