How to add and customize the search box in Magento

form.mini.phtml

//Available at [your-theme]/template/categorysearch/form.mini.phtml
<?php
$catalogSearchHelper =  $this->helper('catalogsearch');
?>
<form id="search_mini_form" action="<?php echo $catalogSearchHelper->getResultUrl() ?>" method="get">
    <div class="form-search">
        <div class="container">
        <input id="search" type="text" name="<?php echo $catalogSearchHelper->getQueryParamName() ?>" value="<?php echo $catalogSearchHelper->getEscapedQueryText() ?>" class="blink" maxlength="<?php echo $catalogSearchHelper->getMaxQueryLength();?>" />
        </div>
        <button type="submit" title="<?php echo $this->__('Search') ?>" class="search-button"><span><span><?php echo $this->__('Search') ?></span></span></button>
        <div id="search_autocomplete" class="search-autocomplete"></div>
        <script type="text/javascript">
        //<![CDATA[
            var searchForm = new Varien.searchForm('search_mini_form', 'search', '<?php echo $this->__('Search entire store here...') ?>');
            searchForm.initAutocomplete('<?php echo $catalogSearchHelper->getSuggestUrl() ?>', 'search_autocomplete');
        //]]>
        </script>
    </div>
</form

gistfile1.php

//Code to add search box
<?php echo $this->getChildHtml('topSearch') ?>