I would suggest you to complete your syllabus first and after that start doing sample papers and previous year papers as these are helpful to know all the important questions and the difficulty level of the exam as well.

Once you are done with these then you can start doing mock papers as these will show where you are standing in your preparation and what all weak areas you are having and these are good to learn time management skills during the exam also.

So if you do the above said things properly then you can crack the exam with flying colours.

Good Luck!!!