There is no secret about doing well in exams… good quality revision and practice, practice, practice…
To this end, click on the link below and it will take you to the OCR website where you can download past papers and their mark schemes.
http://www.ocr.org.uk/qualifications/by-subject/science​

Scroll down and click on SCIENCE (OTHER) this opens another drop down box, from which you can choose from THREE options. You need to find the GATEWAY SCIENCE SUITE – SCIENCE B options which are about two thirds of the way down the list. Any of these are suitable for you to practice from. Select one and then select PAST PAPERS or MARK SCHEMES – the number in the brackets denotes how many past papers or mark schemes are available.