Strike a balance between expositions of other people's views and your own ideas – both are very important elements of an essay.
Another way of putting this is that you cannot write an essay in the space of a week that both provides an exhaustive survey of other people's ideas on a topic and develops your own analysis and arguments to a high level of originality and sophistication. So you need to strike a balance and make compromises. Devote a substantial amount of your essay to explaining what other people have said but also allow a substantial amount for your own criticism and analysis of those arguments, and for developing your own arguments. It is down to you to exercise your own discretion and judgment in deciding exactly how much of each to include.
Make it clear which is which! I sometimes read essays that seem to endorse two entirely opposing arguments. It often emerges that the author of the essay has failed to make it clear when he is expressing his own views and when he is explaining someone else's views. A reader will assume that what she is reading is the author of the essay's own view. If it is not, then make sure it is clear whose view it is and whether or not you agree with it. If your exposition of someone else's argument goes on for several sentences, or even paragraphs, remind your reader that you are still talking about someone else's view with phrases like 'according to Hume' or 'Hume's argument continues' or 'still following Hume's line of reasoning'.
One of the best ways to show that you have understood what you have read and have thought about it clearly (as well as putting other people's arguments into your own words) is to make distinctions between various authors' views (e.g. 'Dawkins' position is subtly different from E. O. Wilson's in that he does not consider co-operativeness to be a natural trait') and between various versions of an argument (e.g. 'The design argument based on the regularity of the laws. of nature is different from the version that focuses on the apparent purpose in nature').
Argumentation not Assertion
In both cases – exposition of others' views and development of your own arguments – views must be argued for and not simply asserted. It is sometimes acceptable simply to state someone's view without explaining or evaluating it in any detail, for the sake of brevity, especially when it is a very well-known view. In most cases, however, especially when the view is your own or is one that you particularly want to endorse or reject, it is essential that you argue logically why it is a good or bad position, rather than just saying that it is.