Do all the questions / practice exams a couple of times over in a quiet place where you can't be interrupted or be distracted. Environment makes a difference so do what works best for you. I spent 3 hours a day at the Uni library just going over every single question in the AFT notes.
Once you get the accuracy work on improving your speed & time yourself. As Nathan says you should be able to do 1 fuel plan in 15-20 minutes. Don't neglect the 3 markers like I did, some of those take as long as the 5 markers & are just as difficult.
I had completed over 100 fuel plans before I was confident to resit. Unfortunately there aren't any short cuts in this exam so repetition is the key.
Good luck.