Do a practise paper and mark it (Or use an example of a mock you may have recently done) and analyse what the reason for each time you lose marks is, eg. is it because you couldn't remember the content?, is it because you made an error in a calculation?, is it because you used the wrong equation?, is it because you knew the content but were unsure how to use it to solve the problem?, etc. Make a tally of which how many marks you lose for each reason. From this you will have a better idea of what you need to focus on to gain more marks.
Hope that helps.
If you discover a significant reason for losing marks but are unsure how to reduce this, feel free to post another question on here asking for advice on that specific area