While all the answers below have truths to them, I didn't notice one factor mentioned that I would consider very important. The price range the house you want, happens to be within. If the list price is more than competitive, and it's less than $400k, there are probably going to be multiple offers, and it likely end up selling for over list price.
If the price is higher than $600k, you can probably negotiate, because there isn't much probability of multiple offers - unless the price is more than 20% less than nearby non-distressed listings. Your agent should know by looking, if a property is "priced to sell".