What are you going to do?

Your primary research might be an experiment, a proof-of-concept prototype, some new insights, a new way of performing, creating or analysing something. Whatever it is, you need to think about how it will look BEFORE you start. How will your academic community look at it? Will they recognise it as an original contribution? How can you convince them it is any good? What counts as being good? – is it being well thought-out, conferring some advantage over current methods, deeper in some sense, more effective in some way?
You need to think first about what tests your community regards as important. Looking at some other contributions in your field, how have they validated or evaluated their contributions? Looking at published reviews or criticisms of other people’s work, what issues excite the interest of the reviewers?
Thinking about such questions will help focus your primary research. Whatever you do, there is little use for messing up. You have one life, and usually just one shot at a full-time PhD. The PhD experience is so much of a trial that you will almost certainly never do another one, though with any luck you will in future supervise many seekers of the way. (Your first successful PhD supervision will be another life-changing experience, but that is a story for another day.)
What would count as messing up? To avoid disaster, think about your sources of data – if there are to be interviews or surveys, choose and plan carefully. If it is an experiment, make sure you think of everything, and calibrate your tools and tests. If it is a prototype, make sure it meets some tangible need and that you have people who understand that need and how to recognise a solution. If it is some new method or technique, make sure it can be compared with existing methods using available or standard comparison techniques.
Once you have answers to all of these questions, look again at your research proposal (prospectus, abstract, manifesto). Does it still look interesting from the viewpoint of a typical member of your academic discipline? If not, you need to go back, and consider how it might be made more interesting, following the rules given in earlier posts.