First off create an essay plan- it's is helpful if you can write down key words in Spanish and try and get you thinking in the language. You should have 3-4 paragraphs with key themes and the argument you want to make. Alongside this, an introduction, in which you want to outline what you are going to be arguing and conclusion in which you want to tie all of your points neatly together.It's good if you can learn Spanish argument phases such as 'en primer lugar' 'es important destacar' 'en conclusión' to provide a clear structure to your essay.Leave yourself plenty of time at the end for checking the grammar; this is very important as often students get carried away with making their arguments that they forget the grammar rules they have learnt.