A PhD level dissertation is an original contribution to the existing body of knowledge. This is the highest level research project in any academic process - by completing a doctoral dissertation you are showing that you are no longer a student, but an independent researcher. Of course, the learning process never stops - not even after completing your PhD dissertation and earning a degree. However, writing and successfully defending your doctoral dissertation signifies that you have covered a long way and are ready to work on your own.
Every doctoral dissertation is essentially a research report, which presents the author's views on a series of problems, concepts, phenomena, - and this view very often relies on the body of knowledge, which was previously developed by other scholars in the same or adjacent field(s). Perhaps the most critical difference between a doctoral level dissertation and a regular research report is that with the latter, you are generally given a question which you have to research. This question is very well known to the person who sets it. Resulting from this, all the parts of such papers, including the literature review part, hypothesis, and (most likely) data, findings, analysis - will all be well know to the person (or a board of persons) who set this assignment. Now, with the doctoral dissertation there is no 'correct answer'. As a matter of fact there can be no correct answer because in the course of writing your doctoral dissertation you will have to research points, ideas and concepts which, have been previously unknown to the public. Yes, the emphasis in this case is laid on originality of the research!
Of course, your work will be reviewed by the experts in the field. They will definitely be knowledgeable on the question of your doctoral dissertation, - yes you should remember that you are the utmost expert when it comes to the narrow topic of your dissertation. No one knows the topic of your doctoral dissertation better than you do. No one in the world.
Once you complete your doctoral dissertation, it will be consulted by scholars from all over the world. For this reason it is important to keep good records of what was done. In addition, the library will keep your doctoral dissertation for future reference and chances are - your doctoral dissertation will be referred to every once in a while. Do not forget to cite properly - you will be committing plagiarism otherwise. Sometimes it may seem extremely tempting to leave the concept without giving the reference, yet giving in to this temptation will prove to be academically fatal. In the era of the Internet and such devices as plagiarism checkers, any instance of plagiarism can be spotted in a heart beat. So while writing a doctoral dissertation (well, this applies to just about any document), it is critical to cite all "borrowed" information.
Style of the doctoral dissertation is another aspect which needs a balanced approach. On the one hand, you need to make the paper simple and communicate the information effectively, while on the other hand you would want to achieve clarity and accuracy of argument.
One important aspect to consider is planning your actions. Planning is an essential step while working on your doctoral dissertation - it prevents you from procrastinating and helps to maintain a sense of a fixed time frame. Before starting to work on a doctoral dissertation, one might think - oh well, the deadline is so far away, - I'll manage. This results in their postponing doctoral dissertation writing till the last minute and quality gets compromised. Developing a schedule, a plan to work by is generally a good strategy.
Writing a doctoral dissertation is a tough work. It is no secret that years spent working on a doctoral dissertation are, perhaps the most strenuous part of their life. Before starting you should know - that in order to make it all through the end, you will need a lot of persistence, patience and diligence. The satisfaction resulting from a successfully completed doctoral dissertation cannot be compared to any other feelings - so on behalf of all scholars - all the best!