Don't bring in extraneous details about the context in which the works were written. Your paper assigments are focussed on a specific topic. Your paper must stick to that topic. For example, "Descartes was a philosopher who was born in France, lived in the Netherlands, and died in Sweden."
Do frame the nature of the philosophical problem clearly. For example, "Is it possible to demonstrate the existence of God using no other information except about what it is to be God?"
Don't go off on a tangent. "Some philosophers have tried to prove that God exists by claiming that the order of nature requires an intelligent designer. Others have thought that the world does not necessarily exist, and if so, then there must be a God which necessarily exists and explains why the world exists. The first kind of argument is called the 'argument from design' and the second kind is called the 'cosmological argument.'"
Do stick to the issues mentioned in the paper assignment.
Don't throw out opinions casually. Example. "How could anybody prove that God exists? That is the kind of things human beings are just incapable of knowing."
Do give reasons for any opinion you express. "Descartes claimed that there is a nature of God. But what evidence is there that there really is such a thing as a nature of God, rather than just a concept of God that we mak up ourselves?"
Don't make undocumented claims about what any of the authors wrote.
Do back up your description of the philosopher's position by use of quotations from the text. Parenthetical page references to the text are sufficient in lieu of footnotes. For example, "According to Descartes, God has a nature and this nature includes existence. He claims that his idea of God's nature is different from a false idea he made up himself, like a four-sided figure that is not a square but is inscribed in a circle. 'For there are a great many ways in which I understand that this idea is not an invention that is dependent on my thought, but is an image of a true and immutable nature' (p. 47)."
Don't use the words of others without quotation. This is plagiarism, which is a punishable academic offense. Your reader will be watching out for plagiarism. One good way to recognize when you are plagiarizing is to notice any change of style, say some sentences which use a lot of words you do not use ordinarily, or whose grammatical structure is very different from your own.
Do use your own words to paraphrase what an author says.
Don't neglect to address all points in the paper topic in detail.
Do provide sufficient detail on all points, so that the grader can recognize your mastery of them.
Don't pad your paper or eliminate vital parts to get it to the suggested length.
Do write economically. Make the paper just long enough to complete the required tasks and no longer. If you deviate significantly from the suggested length, consider whether you have said too much or left something out.
Don't simply write down a bunch of logically unconnected statements or assertions. For example, "Descartes tried to prove that God exists in a couple of ways. Spinoza tried to do the same thing, but he did it differently. Descartes just makes a lot of things up, and Spinoza does too."
Do present the material in the form of arguments. One way of looking at an argument is as the defense of a conclusion by appeal to premises which are acceptable to anyone who considers them objectively, such as that it impossible to think of God except as existing. "From the fact that I cannot think of God except as existing, it follows that existence is inseparable form God, and that for this reason he really exists" (p. 46).
Don't use colloquial language to make a point. For example, "Descartes's second attempt to prove God's existence was totally lame."
Do use standard language.
Don't confuse technical language with ordinary language. For example, Descartes's use of 'nature' is sometimes different from ordinary uses, such as 'part of the earth that is not developed by humans.'
Do explain any technical terms when you introduce them. For example, "The 'ontological argument' is an attempt to prove that God exists simply from the definition, or nature, or idea of God."