Working with Buyer Agent

So I understand working with multiple agents is a no-no, and ethically iffy. But you're also supposed to interview several candidates to find a fit. When are you obligated to work with one person? Are agreements signed during the first meeting, prior to seeing any houses? Or do you meet at a first property and kind of feel the person out then? Are you obligated to pursue that property with that agent, even if you decide not to work with them further? Is it odd cold calling an agent and asking to meet and discuss any available property and how they and their company operates? Thanks