I know home sellers & buyers are using Zillow to get Zestimates but they need to know what they are doing to get most accurate Zestimate. 

When home owners are using Zillow to zestimate their home, they need to do some tweaking to make sure they are getting as accurate as they can.  

They need to verify their home facts are correct by claiming their home on Zillow.  They then need to update their home and make sure the facts are correct.  Once they do this, they can select from the list of homes provided by Zillow that are for sale and sold that are similar to their home so that they can get a more accurate Zestimate.

This holds true for buyers that are wanting to do their own homework on a home they are interested in making an offer on.  If they just look at Zestimate without taking in account the home's features and using the similar comps, they will not get an accurate Zestimate.