More data is not better data. I advise my clients to look for indications of negotiation points, like comparable sales, the seller buying another property, and neighborhood issues that are chasing the seller from their property (this is common if a building project is nearby or the taxes just went up… that kind of thing.)
Here’s a quick primer on how to read Multiple Listing Service (MLS) and alternate real estate listing sites. Most of my clients “web around” to sites like Trulia and Zillow to look at images of properties for sale. We create customized searches with our database, but the raw data is out there for everyone now.