Touch the hat with dirty, oily hands or gloves.There is no quicker way to ruin your hat.
Pick up the hat from underneath by both the front and back brim to maintain the shape and set of the brim. Resting a hat when not on your head on a hat stand or block will make this operation easier.
Resting your hat on any flat surface, especially if it has a snap brim.
To preserve the pitch or scope, of the brim, the lower front of the brim should hang over the edge of any surface it is resting on.
Hats left on a table top bow up in the front and back while bending the sides downward and forever deforming the shape of the brim.
If need be, you can also rest a hat on its crown, providing you place it on a clean surface.
With proper handling and care, a quality hat will remain a thing of beauty and source of pride in any collection or on any head for years to come.