I am struggling with Unit 1 of the GCSE, especially question 4, the 'comparing the use of language in two texts'; how do I improve my marks on this particular question?

Question 4 is the first instance in the paper where a student is required to use more than one source, and again the first question to concentrate in-depth on the effects of language.

I would advise you to first of all step away from the practice papers and the mark schemes and find a 500 word or so text you find enjoyable. This may be a newspaper article or an extract from a novel. Now read this passage two or three times and think about what aspects of it make it interesting. 

It may be useful to think about the following questions. Does the author use special description? Are there some literary devices like metaphors, similes or rhetorical questions being employed? Is there an ironic tone? Is the language factual or emotive?

Don't limit yourself to these - there are many more ways to look at a text!

Once you have got used to the sorts of things you are looking for, move back towards the GCSE questions, it will feel a lot easier than before.

Remember, the emphasis of this particular question is two-fold: can you interpret language and effecitvely compare two different texts (often from different genres)?

This means that you have to talk about effects, backing up your points with specific evidence. Additionally in your answer you must make direct comparisons between each text you have chose - you can only achieve a middle band if your analysis is good, but not comparative. 

Perhaps one way of structuring your answer might be to devote a paragraph to a different effect or aspect of writing. 

Whatever you do, make sure you go back to the text each time you make a point, it makes this exercise a lot less daunting when you realise the skills they are testing are evidence-based, not imagination-based.