Keep it Simple (and Short)
This refers to EVERYTHING, including your argument, your sentences, and your language.
I can understand why undergraduates think that writing needs to be long and complicated. Let’s face it, most of what you are required to read is very long and very complicated. So it makes sense that you think that this is what we require in your writing. But here is the big secret… It isn’t.
If your writing is not simple, then your marker has to spend precious time rereading your work in order to understand what you are trying to say. If this happens, not only do you run the risk of your marker misinterpreting the point that you are making, but s/he end up wasting time, which is bound to make her/him grumpy.
So remember: Paragraphs should always have one (and only one) point to them. Sentences should always be readable in one breath (commas are not always your friend). And words should never need to be looked up in a dictionary.
One trick to achieving all of this is to reread whatever it is that you have written, and delete everything that isn’t central to your story (words, sentences, paragraphs, pages, arguments, etc.). This is often very difficult to do, especially with your own work, and I’m willing to admit that I’m not very good at this myself. However, writing more succinctly is a great way to make your marker very happy!