I was never really any good at writing essays, I never really seen them as that important. But as I got a bit older, and the essays began to equate to something, I decided to start really trying, and I've gotten so into it that I've picked up a few tips here and there.
First thing is, is that whenever you're reading the piece in class before the essay actually comes about, is the literally note down all the quotes you think are relevant and a little page reference.- Writing an essay is tiring enough as it is without having to find all the quotes, so save yourself some time.
Another thing to do during class time would to be to make sure to look at whatever piece you're working on, and look at it from a different perspective.- Instead of looking at it from the character's point of view, look at it from the Author's point of view, and give you're own interpretation of it. Opinion, evidence and evaluate!
Whenever you're writing the essay, have breaks here and there, you're brain can't do it all at once.
Make sure you look at things that happen earlier in the piece, and see if they foreshadow any of the later events. If you can find something that is symbolic and represents something that happens later on, you are on your way to a high grade.
Remember, everything has a more detailed, symbolic meaning to it. Try to look past the obvious, and think about how the author has tried to tie it in with the past, present and future events. Comment on the atmosphere etc, don't just focus on the dialogue.
Also, try and not use the same words over and over, look for synonyms of words you already know- But don't just use any synonym, they are only similar words, they don't mean the same! You could get caught out and look a bit of an idiot, so be careful!