revision help

i don't know what grade you are in but a effective way to revise especially if you know the content is practice past paper exam question, go through the mark scheme and examination comment to see and identify what they are expecting you to write about and the key points for each question

im in y11, and i have decmeber mocks soon! wld u say past papers from memory (because i wont be able to answer half of them i think), or with a revision guide?

Of course you wouldn't have gone through all the topics in year 11, so you won't be able to answer some of the questions in the past paper, but you can still go through some of them.
First, try to do it by memory to identify your gap in knowledge. Afterwards, answer the same questions in a different colour pen using the revision grade.
Finally, correct your answer using the mark scheme.
Try to identify why you got the question wrong. Was it that you were missing the key point, or was it that you didn't have the knowledge. If it was the knowledge part, I will advise you to go through that topic in order to understand the question. However, it was missing the key point; you have to remember those. One way I did it was, in a separate book, I would write the question, or rather, the topic the question was on, and then write the key point. That way, in the future, you can look back on when answering similar questions.
Try using a physics and math tutor to search for the past papers; make sure it is on your exam board. I don't know if the GCSE section has this, but they tend to have questions based on one topic alone that appeared in past paper questions. Those will be good for revision.
This is specific advice for math to revise for math; the most effective way is just going through past papers. Trust me, just do as much as possible; even if you finish them, repeat them again. One thing about math is that the question tend to be the same in all papers but written using different data. So if you stick to just doing papers, you will notice that you will be able to identify what way you are supposed to answer a question and the process would be the same again and again in different papers and before you know it, it will become easy.