What would be a good scenario for a meeting with a potential client regarding a new web app? [closed]

I have an upcoming meeting with a potential client and about a web app for their business. Actually, we already agreed that I will make it for them. Now we will meet again to understand everything from their point of view, what features they need, in other words, understand their as a main daily user needs. This system will be used only by them in their company. This is just the beginning of this process. I really want to get this project right from the UX side (and of course later also the development part) and my question is:

What would be the best process to get all the necessary details from this meeting, so after it, I will know what they need and what to draw?