I have found that an overpriced house actually helps other houses get sold, because they look like an even better value by comparison! I feel it is important to help my sellers to understand who their competition is so we can be the best and most attractive home value in their price range.
There are three places sellers compete. Price, terms and condition. Make sure all three of these are researched and discussed.
In our Minneapolis / St Paul real estate market we have a two week window at the beginning of the listing period to get the highest price. After that time consumers want a discount.
If you have a seller who is not willing to price where you believe the value is, discuss and agree that once you have had 10 showings without an offer it is time for a price reduction down to your price recommendation. Set up this expectation with your seller at the time of the listing agreement. Have scheduled price reductions already agreed upon in the terms of your listing agreement and as part of your overall marketing plan. This makes the price reduction calls so much easier to make and gives your seller a benchmark to measure against.