For the 3 sciences, I suggest SUCCESS reference books. Honestly, these books are really detailed and the explainations in the book is pretty good. I didn't really pay atention in class as my 3 science teachers cannot teach at all. Not to say i'm a professional or anything, but it's true. No one in the class actually pays attention. However, I managed to get A1's for Chem & Bio because of these sucess books. As for Physics, I managed to grab only a B. That's cause I really don't like physics, so.. yeah.
DO MAKE SURE,
1. You understand the particular topic the teacher is talking about. Never EVER accumulate them then try to understand all at one go just before the exam starts. It does not work that way
2. History requires constant reading and understanding. Don't ever rely on all the tips/craps. Just read everything. Some topics are pretty interesting, so just read it before the teacher actually starts teaching them. Then when the teacher starts teaching that topic, you'll find it easier to absorb
3. Do pass year questions. Even though you're only in Form 4, just do them. They aren't tough, and you can roughly know the type of questions that'll be tested

Good Luck.

Nexus Pro is good for Mod maths. Others, please try to use success books. And for history- NO reference books. Read all from the text book The information is more than enough!