Remove post featured image
Go to the content types page on admin/structure/types, click on "Manage display," and drag the field to the "Hidden" set. 



For D6

You can do the same in node-type/&lt;type&gt;/display. Click exclude/ make the select box to hidden. 

Also you can use this code in node.tpl.php.

if ($teaser) { 
  // node is being displayed as a teaser
  // Anything here will show up when the teaser of the post is viewed in your taxonomies or front page
} else { 
  //all other cases
  //Anything here will show up when viewing your post at any other time, e.g. previews
}