I always seem to get stuck on when to use HAS or AS. Is there a simple way in which to remember which word is the correct one?

Grateful thanks,

Has is a form of the verb to have so means "belonging to".
As means "like".

Eg. John has a blue car as does Pete. 
Can you give an example of a case about which you are confused?
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 ALT's reply was promoted to an answer.
Thanks for your clear and precise clarification on this matter. I too have always struggled with Has and As. You are the first person to explain the definition and the context upon which they can be applied.

who has or who as headed paper ?

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