Can't you ask to see their essays, to see what they're doing right that you're not? That's the easiest way; the other way is to do a LOT of reading, spend a LOT of time thinking and basically dedicate your life to that essay for like 4-5 days while writing it. That's what I do, but I think I maybe spend too much time writing them. Then again, I get firsts in all my essays, so maybe this is how it's supposed to be!