At First-Time Home Buyer Tips - Making the Offer | Salary.com
"Experts estimate that most homes sell for about 6 percent less than asking price, but that's just an average and it varies widely from market to market. It's not realistic to expect a seller to go below 5 percent of the list price unless the property has been on the market for a long time and the buyer has set very few contingencies."

At Ask An Agent: How Much Should I Offer Below the Asking Price? |urbanturf.com they say,
"If the price has remained the same on a listing for more than two weeks, we feel it is okay for our buyers to offer a price that is somewhat less than asking, usually around 3 to 5%. If it has been on the market at the same price for two months or longer, we recommend being more aggressive and offering 8 to 10%.
In most cases, a property that has been listed for over two weeks at a given price will sell within 5% of the current asking price (and usually it’s within 3%)

Typical negation with agents making offers on behalf of buyer and seller might go like this.
Buyer offers 6% under listing price.
Seller counters with 2% below listing
Buyer 5%,
Agree on 3.5%
There may be more rounds of haggling.

Examples from Bridgewater - Martinsville Oct. to Dec. '17

Try to get a buyer that is pre-approved rather than just pre-qualified.
Pre-Qualified just means someone has asked for your income over the phone to see if it will cover loan payments.
Pre-Approved means the buyer has completed a mortgage application (usually with a fee) and their financial background and current credit rating have been checked to get approved for a given mortgage amount.
The bank will still have to have an appraisal to finalize the loan.

Realtors will tell you if you list at a lower price you are more likely to have a bidding war and the selling price will be more than tha asking price.
Bidding wars don't usually happen unless you are in a "hot" marked with low supply and high demand.

The first offer is the best offer:
This a standard mantra from real estate agents.
In the article below they say it may well be true and list some cases where that may be true, but they say they have also seen many cases where the buyer held out and got a better price. Source: Your First Offer Is Your Best Offer - Fact Or Fiction? - Getting Real

Some Comps:

813 Miller Ln. 3,983 sf, 1.15 acres  5 beds, 3.5 baths


Assessed $646,100 2017
Listings
6/13 $799,000
2/15 $699,900
6/16 $649,000
9/17 sold $620,000