My best tip:
CGP Revision guide for Sciences. They are the work of GODS i tell you. The way they word their material= how you should word them in the exam. Literally- easy A*. Read through all the material atleast 3 times before the exam comes up (with 1 week between each reading). B1, B2 and B3 is LINKED (same for other sciences and their respective units). You can easily capitalise on this. B1 is very simple and sounds like common sense. Once you know this and know the exam technique well. Start looking at related topics in B2 and B3. B2 feels like it has the most content and B3 is by far the one with the most depth. But memory is based on being able to link different ideas together. Cover the linked topic (like homeostasis in B2 and B3), therefore it feels more like an expansion on the initial knowledge and less content heavy. Furthermore, certain topics in Biology are linked to the ones in Chemistry and Physics. Climate change is an important one, as well as biogas/biofuels. Try to explain this stuff to yourself--Since it all makes sense on a logical viewpoint.
Past Papers and Mark scheme= You can maximise marks as many of the same questions come up with the exact same answers. It will really teach you the exam technique you need to ace the tests. Do a past paper in timed conditions. Mark it (be harsh). Understand your mistakes and remember it.
MyGCSEScience is good- but he takes wayy too long to explain a topic that you can read in a few minutes and do some questions on. Plus his voice makes me a bit sleepy <.<