One thing to remember when writing philosophical essays is that it is very important to be as clear as possible. Let's face it, philosophy is difficult, full of categorical imperatives and hard problems of consciousness. To compensate, make your language as clear as possible. If you can describe a complicated idea or concept with simple language, then whoever is marking your essay will be able to see that you GET it. Of course, sometimes technical words are called for, like a posteriori, a priori, ceteris paribus, syllogism, tautology, non sequitur, etc. But use these with care and only when appropriate. Employing selected philosophical terms well will impress the examiner, using them incorrectly will make them sigh. In general though, keep to Orwell's maxims and make your essays clear and crisp.