if you ever decide you want to work with a property manager let me know. i am a Realtor/Property Manager with Copper Rose Realty. We have been doing this for years before everyone else jumped on the bandwagon. there are certain sites we use to determine rents. jennifer tillman 520-203-1572
The rental market is extremely hot right now, so I would say that the fact that you had so many people calling you might not necessarily mean that you underpriced it. You can check out my most recent blog here on trulia about how hot the market is and how people should buy now if they can. :)
I would definitely do my research though. I also do property management and I always do a thorough study of what my current competition is renting for and what is already rented. I would check out Craigslist for other rentals in your area OR if you have a real estate agent that you work with, they can check the local MLS for you.
Congrats- Hope you signed a lease and got a good tenant!