If you have an understanding and I truly emphasise on this, the learning becomes natural. There are times where you may be required to memorise such as English. I remember when my half yearly examination for form III gave us the question beforehand and obviously, it's best to have a draft answer prepared. My technique: Write out the essay and edit it. After that, make a copy of that paper but with dot points and simply read and understand the question asked. When you know your arguments, it should be a lot easier. None of this writing excessively on the paper until your brain memorises it.