How to choose a research topic

There are TWO THREE important things to keep in mind.

Firstly, ask yourself the following questions:

1. What interests me?
2. What do I want to do for a living in the near future?

You answers to the above questions could give you first hints on what you are passionate about and what knowledge/skills are indispensible for your future career. With this information, you could then have a better understanding of your research interests. It would be great if the topic you will be working on during your MEng or PhD study is linked to your future career directly. But this is not alwasys possible and not necessary. As long as the methodologies involved in the topic are applicable to your envisioned work environment, you are good.

Secondly, check out the research interests of your supervisor if you already have one (very important). This is to make sure that you do not work on something your supervisor is unable/unwilling to provide guidance.

Lastly, take a look at the following slides from Marek J. Druzdzel to get an idea about what makes a good topic: How to Identify a Good Research Topic? (A personal view).

How specific do I need to be

There is no standard rule of telling this. The general rule is that the research question you have chosen must be of scientific merit, application relevance, and narrow enough to be solved within your available time and resources.