When revising a character the most important thing to do is re-read the sections of the novel they appear in with the aim of being able to answer certain key questions about the character. For example, for questions of the style "consider the importance of x in novel y" they key questions you want to be able to answer are things like 'what is the timing and context of the characters appearance in the novel,' 'can the character be taken as representative of an important group or idea in the novel' (I would spend more time discussing how to analyse this) and 'what is the characters role in the plot.' Being able to answer these sorts of questions naturally gives a strong base that can be applied to more specific questions about the character - once you have a clear idea about when and in what circumstances the character appears, as well as how they fit into the wider narrative, this idea can be applied to lots of different types of question. Another essential aspect of understanding a character is considering how they have changed throughout the novel (this can often be an essay question in itself). For this style of question the main things to consider are the nature of any changes - are they merely superficial or do the characters attitudes or ways of life significantly change - and whether these changes are positive or negative in the context of the novel. Essays about whether a character has changed or not can be particularly sharpened by a consideration of what change or its failure means in the wider context of the novel. To give an example of this, an essay which argued not just that Lady Catherine in Pride and Prejudice does not change, but that this failure to change indicates the conservative nature of the old aristocracy that she originates from symbolises and therefore the wider conservatism of that group would be significantly stronger. Once again a clear idea of the characters role in the novel allows for stronger answers.In practical terms the main revision techniques I would recommend are re-reading the sections of the novel the character is in, learning key quotations from or about the character and planning essays. Even if the essay in the exam is not one you have planned writing a variety of plans about the character will get you thinking about them and how they interact with the novels plot, character and themes, naturally improving your understanding of the novel.