A dissertation is a structured essay, which works to help a student learn about a topic in most cases. It is also an indicator of how well the student is doing. Sometimes a dissertation is one of the things that makes a big difference in the final grade of the student. It is a highly independent piece of work, which involves a student going out and studying the topic they choose. They must research into the topic; create a thesis, arguments, analysis and conclusion.
Sometimes people do struggle, in which case they can contact a service such as dissertation-service.org. In most cases the research and writing services that dissertation-service.org provides is enough to ensure a good grade for the student. A research paper and a dissertation are pretty much the same thing except for that a dissertation has fewer rules as to how it is written. It is an independent study process. The written side to a dissertation is nothing more than a record of study which has been organized and structured so that it contains arguments, a thesis, reasoning and conclusions. It is a way of showing the world what you found out and why. In a way it allows you to share your experiences so that other people don't have to take up the task of doing their own dissertation on the subject. It however must be structured so that it fit's the subject you are learning. There is no point in following research methodology for biology if you are studying French.
The best way to pick a dissertation topic is to use the MORI principle. MORI was developed to help students pick their dissertation topics. It stands for Manageable, Original, Relevant and interesting. Those are four principals that will help you to get the top marks on your dissertation.
Make your workload manageable. There are some fine topics for dissertation out there which are exciting, original and new. However, to fully cover them in a dissertation it would take years, some topics are simply too big for a student to cover. Manageable does not only cover time, it also covers expense. Some of the more original dissertation topic ideas will involve a bigger budget that most students have access to.
Originality is one of the more obvious points in a dissertation. Not only in the content itself (don't plagiarize) but also in the topic for dissertation. The topics that are too easy or have been covered comprehensively by other people are not going to win you the highest marks. You need to think of something original (at least in part) otherwise, your dissertation will not stand out enough to get full marks.
Relevancy is also important because you are studying a certain subject. It would make no sense to study astrophysics, only to do a dissertation on quantum theory. You must keep your topic relevant. How interesting your topic is, is a matter of opinion in some respects. The dissertation text will no doubt have to be very dry, but there is nothing wrong with picking an exciting topic.