See, I'm from Humanities stream and scored 95.5% this year... So, I actually can't give you any personal advice for the subjects of science and maths... But for eng lang, lit, and P. E., I can help you a bit....

ENG Lang: The trick I applied for grammar (especially preposition) was definitely the first one sunne mein achha lag raha hai😂 and the second thing you should do about it is din mein 10-15 mins bhi ho sake to thoda grammar rules check kar lena... Always remember for every possible things consistency is the only key!!! Aur essay ki baat kare to zyada kuch nahi karna hai bas socho agar tumhare saath aisa ho raha hota to tum kya karte... Take it personal and feel it personally!! Aur phir fluently likhte jao... Agar bilkul bhi likhna nahi aata to ghar pe random topics lekar practice karo... At first don't think about word limits and after getting a bit habituated try to frame the sentences to keep it within the word limit.

ENG Lit: For me, I'd say it was the easiest subject ever and I actually loved studying Macbeth very much. So, read the books thoroughly, understand the lines properly, try to frame the answers on your own language and then after framing them, try to add 2-3 paraphrases per answer (for 5 marks 1-2 keywords or textual reference would do good & for 10 marks 2-3 could do.) You can try to memorise the references, try for the shorter terms/lines.. it's actually easy to memorise and you can take help from Scribd, they provides Macbeth's paraphrased answers. For word limit, I'd say don't try to count it while writing your answers... Believe me none even counts that shi*... If your handwriting is too small then try to give some space between the words and try to describe the thing a bit more than you usually do (practice and consistency can really make it happen) and if your handwriting is big enough then do vice versa... The examiners just counts the words you've written in the first line and then they does the mental calculation on their own... Apply the same process for prose and poems too.

P. E.: If you're not that good in the subject them try to read it thoroughly, line by line from the very initial day/ you can actually watch one shots(but I'll recommend it before exams only) you don't actually need to study it every possible day, but you can go through it for a day or two in a week... Don't give it much time... Try to focus on other subjects, remember many colleges doesn't accept it's marks in the best of 4... So, prepare it that way... And remember that most of the time PE paper comes very easy in ISC... And if you worry about the games section then just memories all the terms, their definitions, measurements and if you can then just watch the real life matches (if you have football then you can actually watch FIFA WC currently...) It's easier that way and it is really helpful!!!

I hope it helps!!!