Set default text for the_search_query();

Do not hard code a value in the search field. You will get a lot of nonsense searches because people do not expect that they have to clean up the field before they can actually type something into it. They will just type and hit enter.

Alternatives:

  1. Use the placeholder attribute. You can style it separately.

    <input placeholder="<?php _e( 'Search' ); ?>">
    
  2. Use nothing. If your users need a text inside of the field to realize that it is a search field your page design is broken. Fix the design, don’t add clutter.