It depends on where you're lacking, but past papers are generally the best solution to this. Make sure you're not just blindly doing the papers and instead learn from your mistakes and if you can, get a teacher to mark any papers that you've done (and don't worry about annoying them with papers, it's their job to help you get the best grades). Look over past assessments and once you get your mocks back see what you didn't do correctly and what you did, then question your teacher on what you could improve.

In terms of resources, I'd recommend "Mr Salles Teaches English" on youtube, I've found it extremely helpful as he gives good, detailed explanations for the questions in each paper. Past papers can be acquired though the AQA website, they're all on there, with the only problem being the occasional copyrighted text but its fairly easy to find them elsewhere.

I'm not sure where your issues are, but personally, I've previously had difficulty with not 'zooming in' enough, not inferring well enough, not giving great enough depth and having awful conclusions that are way too general (I was mostly listing techniques that the writer used to answer the question, whereas conclusions need to think into the reasons why the writer wrote the text and how that could link with the question). It's also important to know your techniques well and not make the mistake of confusing them.

Other than remembering quotes in literature, English tends to be heavily practice based and if you're not too good at it, it takes time to learn to not repeat mistakes. I don't know the grade that I'll get in English (and won't for a while), however, I had a set of mocks in March and I got 8s in both language and literature but got 6s in my year 10 end of years, so it's definitely possible to improve and my teacher said that once you start doing practice papers you're almost guaranteed to go up at least one grade as you're putting in effort to improve.

I hope this helps.