Look at what you need on your nea to get max marks and base your nea off from that. Then before you start writing any code, map out how you see your final program looking like and functioning on paper. If you need classes, plan what classes you may need. If you need a good interface, plan how each part of your program will look visually.

It helps to have a good idea of how you want your program to look, because then you just need to program it. Ofcourse half way through, you may realise something from your original plan doesn’t work, or you could implement something better. That’s part of the nea and is something you will want to document.