i actually marked a lot of essays on VN, and read the criticisms of others on the same essays
if you see a quote thats rarely used, write it down and hang it in front of your desk

i felt that helped me to remember the tricky ones
i also on read from sparknotes, but that was only on 2 occasions leading into a SAC
you dont want to write too many essays early on or else you'll fizz out by then time exams come. maybe 2-3 practise ones leading into a SAC, otherswise one a week + school assigned work should suffice. reading your texts well is obvious, noting the key quotes, themes, symbolism ect.
hmm thats all i can really think of right now, but i would strongly advice reading the essays of others and trying to identify faults, before attemping your own rendition of the prompt. i felt that contributed most towards my A+

good luck!
EDIT: you want your writing at its peak from the first SAC, perhaps a tutor if you feel as though your writing is not adequate, otherwise submit essays for correction here, im sure we'd all be glad to assist you

my mistake was my writing peaking in October so my GAs only read B+ A A+ for 38. more SAC preparation and less dillusion would have allowed me to get the 42+ i expected.