Be realistic when it comes to what you can expect from your supervisor. Amongst all their other responsibilities, supervisors will only have a small amount of time to provide support, especially if you're an undergraduate or master's level student. At the same time, although it's not great to have to say it, not all supervisors are willing to give up their time, or provide much help, even when they do have time. Therefore, you really need to get the most from your supervisor when you do meet them. Expect to have no more than 20 minutes to put forward your topic idea and get feedback (any more is a bonus).
Supervisors will seldom give you the answers you want directly. You'll also often find that they answer questions with questions, which can be annoying. However, if you have a sympathetic supervisor, some of the following questions may be useful at this stage:
Problems with the idea:
Are there are any flaws in the logic behind the duplication, generalisation or extension that I have put forward?
Problems implementing the idea:
Can you see any major barriers to carrying out a dissertation based on the proposed topic?
People that could help:
[If your supervisor is not an expert in your topic area]
Are there any academics within the department that you think I should talk to about my topic?
All you really want to know from asking these questions is whether there are any major roadblocks that could hamper your proposed dissertation.
Your supervisor might want to know more about (a) the constructs and variables that you are interested in, and (b) your proposed research strategy (i.e., everything from the research design through to the research methods, sampling strategy, and so forth). At this point, you are unlikely to know much about either (a) or (b) because you have yet to build the theoretical case (i.e., STAGE FIVE) or determine the research strategy (i.e., STAGE SIX) for your dissertation. However, it is a good idea to go into this initial meeting knowing the constructs and variables used in your main journal article, as well as the research strategy that was originally used. If you are pursuing a method and measurement-based extension or a design-based extension under Route C: Extension, it is important to have a better sense of the research strategy you plan to pursue at this stage. In this case, you may find it necessary to briefly go through STAGES FIVE and SIX before meeting with your supervisor.