You might like to ask to see a copy of the rental agreement and condition form (though they will probably give it to you without asking).
Ask if they take photos for advertising, how much they charge for advertising and where they advertise.
Ask about their process for selecting and what your options are for discrimination (ie no pets or specify pets)
Ask about how often they have had to go to the tribunal (i think that is the right term...where disputes are heard) and how that usually goes.
Do they take photos at inspections?
ask about the landlords insurance. (for advice)
Ask about any extra costs beyond the % fee.

In talking with them, use your gut.
You want this property to be someones home, but it is still your house. So the agent needs to respect the tentant, but be your advocate. A though inspection is important.

And ask about maintance...if you want to you can opt to do handy-person stuff, but you have to be prepared to do it quickly.
So ask about the rights of tenants, and what your obligations are by law in regards to maintance. Who changes/supplies light globes, who mows. prunes, what happens if the hotwater fail, or the dishwasher breaks. That sort of thing.

all the best
Catherine