Q: Wordpress search custom form I have standard search form in on my WP.
<form method="get" id="searchform" action="<?php echo esc_url( home_url( '/' ) ); ?>">
    <label for="s" class="assistive-text"><?php _e( 'Search', 'twentyeleven' ); ?></label>
    <input type="text" class="field" name="s" id="s" placeholder="<?php esc_attr_e( 'Search', 'twentyeleven' ); ?>" />
    <input type="submit" class="submit" name="submit" id="searchsubmit" value="<?php esc_attr_e( 'Search', 'twentyeleven' ); ?>" />
</form>

How can I do this?

A: Simply create a searchform.php in your theme-folder.
Copy the php-tags from the standard code, to achieve similar behaviour. Also don't change the name-attributes, or it won't work.
<form role="search" method="get" id="searchform" action="<?php echo home_url( '/' ); ?>">
  <div><label class="screen-reader-text" for="s">Search for:</label>
    <input type="text" value="" name="s" id="s" />
    <input type="submit" id="searchsubmit" value="Search" />
  </div>
</form>

See the example on this Codex page
