Etiquette for establishing contact with multiple professors for PhD guidance
Advisors understand that students are fishing around - that's normal. What's less common (but possible) is students fishing around in wildly different areas. Just keep in mind that either an advisor is going to see something in you that will motivate them to try and convince you to work with them, or they'll view you as someone who needs to make up their mind first, and won't spend too much time thinking about you. 

In that respect, matching up with an advisor is more like dating than an job interview, at least in the US :)