It's a mix of preparation, prayer and luck really. I don't consider myself to be as proficient in English as my scores may depict. I prepared heavily for two weeks leading up to my first attempt but only prepared for few hours before the 2nd attempt and ended up getting much better scores in the 2nd attempt. I believe luck also plays a part as I may have gotten lower scores if I got a tricky map in listening section, a tricky topic for essay or a grumpy examiner in speaking. However, it so happened that everything went right on that day. BUT, you still need to put in the bare minimum hard work necessary to score CLB 9 to be lucky enough to cross into CLB 10 if your English is not that great. My personal tips for you are as follows:
1) Read books if you are weak in reading. Listen to stuff on the internet (like PMQs) if you're weak in listening.
2) Strengthen reading and listening as if you consistently score 36+ in your home tests, you're 99% sure to get 36+ in the tests. Both of these modules are like Maths as scores are kinda guaranteed if you are good enough.
3) Get your writing checked by a Cambridge examiner (not just an English teacher). They will advice you on improving. Look up Tony Grace as he's great at helping you improve even though on the expensive side.
4) For speaking, your prep in other modules will help you increase your armory of words and ideas. Try to speak with a native speaker and record yourself while answering questions and do self analysis. Make it a habit to speak after thinking out the sentence in your mind first. Try to be correct without taking shortcuts that ruin our language.
Hope this helps! Good luck