In short, ask a Realtor for a Competitive Market Analysis (CMA). 

It will show you what comparable homes in your neighborhood have sold for recently (the most critical number) and the list price of similar homes currently for sale. 

Much as we would like to think we can set the selling price of our home, in fact it is the market that sets the price.  Pardon the comparison, but it's no different than used cars - worth what someone will pay.   That's why the key number is what comparable homes have actually sold for. 

Remember that every buyer will have the same numbers available as your Realtor gave you. 

You needn't sell your home for the average comparable sold price.  You may get more if your home has unusual value-adding features (newly remodeled kitchen, extra large lot, view, etc.), but the reverse is also true.  If your home has a 1960's kitchen, small lot and view of the back side of an apartment house, you will likely get less than average.   A good Realtor can advise you on all those (and other) pricing issues.