The secret to english success is that there is no secret. It's all about crafting ad hoc responses, integrating detailed knowledge of your texts, that adequately address the question. Memorised essays are not the way to go, unless you've been given the exam question beforehand. All I've ever done is know my texts inside and out and memorise key sentences or paragraphs for a general essay-type question - the rest comes on the day, in the exam room. An extensive vocabulary, wide reading experience (both fiction and non-fiction) and knowledge of correct grammar are also invaluable.
I'd be wary of getting a tutor. By all means, go for it, but don't get caught in the trap of having an english tutor that simply edits - or worse, writes - essays for you. Make sure he or she perfects your exam technique and increases your knowledge of subject matter, otherwise you're not getting your money's worth.