Questions on finding property value

[Jared G.]

Let's say there's a property I'm interested in and I want to know what it should be valued at. Point blank: how do I know? What I have heard and read is compare it to similar properties in the same area that have been sold recently. Where do I find this information? I know that Zillow, Trulia, etc. are NOT accurate for knowing the property's value -- but what about already sold ones? 

If the comparable properties have small differences (number of rooms, square footage), how do I know how much to take off or add on to my potential price?

Assume that I am not ready to buy and am only doing this to get a feel for a neighborhood -- would it still make sense to contact a realtor? Can any of this be done accurately without one? I don't want to waste their time when I have no intention on buying for a while.

What else do I need to know?