Above all else, academic writing is scientific writing. That means it does not necessarily have to be particularly original, nor does it have to have a lively and engaging style - those are characteristics which you can leave to creative writing, or other genres of factual writing.
Academic writing is designed to convey a synthesis of your research, something which explains many of the distinctive features with which you may be unfamiliar, such as the use of referencing and the need to give a bibliography. Successful academic writing enables somebody who lacks familiarity with a subject not only to acquire facts about it, but also to understand the kind of approach you've taken to the subject, and to know what your sources are.
Academic referencing systems are designed to take care of the problem of indicating sources. Conveying information to your reading audience, though, takes more thought, as you need to decide what levels of detail will add to your audience's already existing knowledge - overwhelming your audience with too much detail is as bad as repetitively telling people what they already know. Enabling your audience to understand the approach you've taken to the subject is probably the most difficult aspect of academic writing, as in order to do this you need to examine your own writing process by engaging in reflective practice- provided you've taken care of the other elements, doing this will gain you the most marks.