Don't combine checkout steps into a single crowded step

Don't overwrite Magento's functionality

Don't weigh down your checkout page

Don't trust anything but numbers

Look for an alternative

Links mentioned in this post:

• Google Website Optimizer
• A/B Testing the One Step Checkout Magento Extension
• Magento Conversion Rate Optimization – Cart and Checkout
• Optimized Checkout Extension
• Newsletter Checkout Extension

app/code/core/Mage/GoogleAnalytics/Block/Ga.php

    /**
     * Render GA tracking scripts
     *
     * @return string
     */
    protected function _toHtml()
    {
        if (!Mage::helper('googleanalytics')->isGoogleAnalyticsAvailable()) {
            return '';
        }
        $accountId = Mage::getStoreConfig(Mage_GoogleAnalytics_Helper_Data::XML_PATH_ACCOUNT);
        return '
<!-- BEGIN GOOGLE ANALYTICS CODE -->
<script type="text/javascript">
//<![CDATA[
(function() {
var ga = document.createElement(\'script\'); ga.type = \'text/javascript\'; ga.async = true;
ga.src = (\'https:\' == document.location.protocol ? \'https://ssl\' : \'http://www\') + \'.google-analytics.com/ga.js\';
(document.getElementsByTagName(\'head\')[0] || document.getElementsByTagName(\'body\')[0]).appendChild(ga);
})();

var _gaq = _gaq || [];
' . $this->_getPageTrackingCode($accountId) . '
' . $this->_getOrdersTrackingCode() . '
//]]>
</script>
<!-- END GOOGLE ANALYTICS CODE -->';
    }
}

    /**
     * Render GA tracking scripts
     *
     * @return string
     */
    protected function _toHtml()
    {
        if (!Mage::helper('googleanalytics')->isGoogleAnalyticsAvailable()) {
            return '';
        }
        $accountId = Mage::getStoreConfig(Mage_GoogleAnalytics_Helper_Data::XML_PATH_ACCOUNT);
        return '
<!-- BEGIN GOOGLE ANALYTICS CODE -->
<script type="text/javascript">
//<![CDATA[
var _gaq = _gaq || [];
' . $this->_getPageTrackingCode($accountId) . '
' . $this->_getOrdersTrackingCode() . '

(function() {
var ga = document.createElement(\'script\'); ga.type = \'text/javascript\'; ga.async = true;
ga.src = (\'https:\' == document.location.protocol ? \'https://ssl\' : \'http://www\') + \'.google-analytics.com/ga.js\';
var s = document.getElementsByTagName(\'script\')[0]; s.parentNode.insertBefore(ga, s);
})();
//]]>
</script>
<!-- END GOOGLE ANALYTICS CODE -->';
    }
}

Tracking across sub domains

_gaq.push(["_setAllowHash", false]);

	/**
	 * Added to fix cross sub-domain tracking issue
	 */
	public function getDomainName()
	{
	$removepre = array ("http://","/","www","secure");
	if (!$this->hasData('domain_name')) {
		$this->setDomainName(str_replace($removepre, "", Mage::getBaseUrl()));
	}
	return $this->getData('domain_name');
	} 

_gaq.push(["_setDomainName", "' . $this->getDomainName() . '"]);

	/**
	 * Added to fix cross sub-domain tracking issue
	 */
	public function getDomainName()
	{
	$removepre = array ("http://","/","www","secure");
	if (!$this->hasData('domain_name')) {
		$this->setDomainName(str_replace($removepre, "", Mage::getBaseUrl()));
	}
	return $this->getData('domain_name');
	} 

    /**
     * Render GA tracking scripts
     *
     * @return string
     */
    protected function _toHtml()
    {
        if (!Mage::helper('googleanalytics')->isGoogleAnalyticsAvailable()) {
            return '';
        }
        $accountId = Mage::getStoreConfig(Mage_GoogleAnalytics_Helper_Data::XML_PATH_ACCOUNT);
        return '
<!-- BEGIN GOOGLE ANALYTICS CODE -->
<script type="text/javascript">
//<![CDATA[
var _gaq = _gaq || [];
' . $this->_getPageTrackingCode($accountId) . '
_gaq.push(["_setDomainName", "' . $this->getDomainName() . '"]);
_gaq.push(["_setAllowHash", false]);
' . $this->_getOrdersTrackingCode() . '

(function() {
var ga = document.createElement(\'script\'); ga.type = \'text/javascript\'; ga.async = true;
ga.src = (\'https:\' == document.location.protocol ? \'https://ssl\' : \'http://www\') + \'.google-analytics.com/ga.js\';
var s = document.getElementsByTagName(\'script\')[0]; s.parentNode.insertBefore(ga, s);
})();
//]]>
</script>
<!-- END GOOGLE ANALYTICS CODE -->';
    }
}

<?php
/**
* Magento
*
* NOTICE OF LICENSE
*
* This source file is subject to the Open Software License (OSL 3.0)
* that is bundled with this package in the file LICENSE.txt.
* It is also available through the world-wide-web at this URL:
* http://opensource.org/licenses/osl-3.0.php
* If you did not receive a copy of the license and are unable to
* obtain it through the world-wide-web, please send an email
* to license@magentocommerce.com so we can send you a copy immediately.
*
* DISCLAIMER
*
* Do not edit or add to this file if you wish to upgrade Magento to newer
* versions in the future. If you wish to customize Magento for your
* needs please refer to http://www.magentocommerce.com for more information.
*
* @category    Mage
* @package     Mage_GoogleAnalytics
* @copyright   Copyright (c) 2010 Magento Inc. (http://www.magentocommerce.com)
* @license     http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)
*/


/**
* GoogleAnalitics Page Block
*
* @category   Mage
* @package    Mage_GoogleAnalytics
* @author     Magento Core Team <core@magentocommerce.com>
*/
class Mage_GoogleAnalytics_Block_Ga extends Mage_Core_Block_Text
{
    /**
     * @deprecated after 1.4.1.1
     * @see self::_getOrdersTrackingCode()
     * @return string
     */
    public function getQuoteOrdersHtml()
    {
        return '';
    }

    /**
     * @deprecated after 1.4.1.1
     * self::_getOrdersTrackingCode()
     * @return string
     */
    public function getOrderHtml()
    {
        return '';
    }

    /**
     * @deprecated after 1.4.1.1
     * @see _toHtml()
     * @return string
     */
    public function getAccount()
    {
        return '';
    }

    /**
     * Get a specific page name (may be customized via layout)
     *
     * @return string|null
     */
    public function getPageName()
    {
        return $this->_getData('page_name');
    }

    /**
     * Render regular page tracking javascript code
     * The custom "page name" may be set from layout or somewhere else. It must start from slash.
     *
     * @link http://code.google.com/apis/analytics/docs/gaJS/gaJSApiBasicConfiguration.html#_gat.GA_Tracker_._trackPageview
     * @link http://code.google.com/apis/analytics/docs/gaJS/gaJSApi_gaq.html
     * @param string $accountId
     * @return string
     */
    protected function _getPageTrackingCode($accountId)
    {
        $pageName   = trim($this->getPageName());
        $optPageURL = '';
        if ($pageName && preg_match('/^\/.*/i', $pageName)) {
            $optPageURL = ", '{$this->jsQuoteEscape($pageName)}'";
        }
        return "
_gaq.push(['_setAccount', '{$this->jsQuoteEscape($accountId)}']);
_gaq.push(['_trackPageview'{$optPageURL}]);
";
    }

    /**
     * Render information about specified orders and their items
     *
     * @link http://code.google.com/apis/analytics/docs/gaJS/gaJSApiEcommerce.html#_gat.GA_Tracker_._addTrans
     * @return string
     */
    protected function _getOrdersTrackingCode()
    {
        $orderIds = $this->getOrderIds();
        if (empty($orderIds) || !is_array($orderIds)) {
            return;
        }
        $collection = Mage::getResourceModel('sales/order_collection')
            ->addFieldToFilter('entity_id', array('in' => $orderIds))
        ;
        $result = array();
        foreach ($collection as $order) {
            if ($order->getIsVirtual()) {
                $address = $order->getBillingAddress();
            } else {
                $address = $order->getShippingAddress();
            }
            $result[] = sprintf("_gaq.push(['_addTrans', '%s', '%s', '%s', '%s', '%s', '%s', '%s', '%s']);",
                $order->getIncrementId(), Mage::app()->getStore()->getFrontendName(), $order->getBaseGrandTotal(),
                $order->getBaseTaxAmount(), $order->getBaseShippingAmount(),
                $this->jsQuoteEscape($address->getCity()),
                $this->jsQuoteEscape($address->getRegion()),
                $this->jsQuoteEscape($address->getCountry())
            );
            foreach ($order->getAllVisibleItems() as $item) {
                $result[] = sprintf("_gaq.push(['_addItem', '%s', '%s', '%s', '%s', '%s', '%s']);",
                    $order->getIncrementId(),
                    $this->jsQuoteEscape($item->getSku()), $this->jsQuoteEscape($item->getName()),
                    null, // there is no "category" defined for the order item
                    $item->getBasePrice(), $item->getQtyOrdered()
                );
            }
            $result[] = "_gaq.push(['_trackTrans']);";
        }
        return implode("\n", $result);
    }

	/**
	 * Added by noam to fix cross sub-domain tracking issue
	 */
	public function getDomainName()
	{
	$removepre = array ("http://","/","get","secure");
	if (!$this->hasData('domain_name')) {
		$this->setDomainName(str_replace($removepre, "", Mage::getBaseUrl()));
	}
	return $this->getData('domain_name');
	} 

    /**
     * Render GA tracking scripts
     *
     * @return string
     */
    protected function _toHtml()
    {
        if (!Mage::helper('googleanalytics')->isGoogleAnalyticsAvailable()) {
            return '';
        }
        $accountId = Mage::getStoreConfig(Mage_GoogleAnalytics_Helper_Data::XML_PATH_ACCOUNT);
        return '
<!-- BEGIN GOOGLE ANALYTICS CODE -->
<script type="text/javascript">
//<![CDATA[
var _gaq = _gaq || [];
' . $this->_getPageTrackingCode($accountId) . '
_gaq.push(["_setDomainName", "' . $this->getDomainName() . '"]);
_gaq.push(["_setAllowHash", false]);
' . $this->_getOrdersTrackingCode() . '

(function() {
var ga = document.createElement(\'script\'); ga.type = \'text/javascript\'; ga.async = true;
ga.src = (\'https:\' == document.location.protocol ? \'https://ssl\' : \'http://www\') + \'.google-analytics.com/ga.js\';
var s = document.getElementsByTagName(\'script\')[0]; s.parentNode.insertBefore(ga, s);
})();
//]]>
</script>
<!-- END GOOGLE ANALYTICS CODE -->';
    }
}

{{block type="catalog/product_new" name="home.catalog.product.new" alias="product_homepage" template="catalog/product/new.phtml" _productsCount="8" cache_lifetime="1"}}

a:5:{i:0;s:69:"Invalid method Mage_Wishlist_Block_Links::addWishlistLink(Array
(
)
)";i:1;s:2313:"#0 [internal function]: Varien_Object->__call('addWishlistLink', Array)

<reference name="top.links">
    <block type="wishlist/links" name="wishlist_link">
         <action method="addWishlistLink"></action>
    </block>
</reference>

<reference name="top.links">
    <block type="wishlist/links" name="wishlist_link"/>
    <action method="addLinkBlock"><blockName>wishlist_link</blockName></action>
</reference>

{{block  type="catalog/product_new" name="home.catalog.product.new"  alias="product_homepage" template="catalog/product/new.phtml"  _productsCount="9"}}

<select onchange="setLocation(this.value)">
	 <option value=""><?php echo 'Choose an Option...' ?></option>
<?php foreach ($this->getItems() as $_item): ?>
    <option
        <?php if ($_item->getCount() > 0): ?>
        value="<?php echo $this->urlEscape($_item->getUrl()) ?>"><?php echo $_item->getLabel() ?>
        <?php else: echo '>' . $_item->getLabel() ?>
        <?php endif; ?>
        (<?php echo $_item->getCount() ?>)
    </option>
<?php endforeach ?>
</select>

<reference name="left">
	<remove name="cart_sidebar"></remove>
	<remove name="catalog.compare.sidebar"></remove>
	<remove name="sale.reorder.sidebar"></remove>
</reference>

$result = imagejpeg($object->getTmpImage(), $object->getFilePath(true), 80);

$result = imagejpeg($object->getTmpImage(), $object->getFilePath(true), 95);

Add Home Link To The Menu Bar

<div class="header-nav-container">
	 <div class="header-nav">
		  <h4 class="no-display"><?php echo $this->__('Category Navigation:') ?></h4>
		  <ul id="nav">
 
		  <!-- HOME BUTTON HACK -->
		  <?php $_anyActive = false; foreach ($this->getStoreCategories() as $_category) { $_anyActive = $_anyActive || $this->isCategoryActive($_category); } ?>
		  <li class="<?php echo !$_anyActive ? 'active' : '' ?>"><a href="<?php echo $this->getUrl('')?>"><?php echo $this->__('Home') ?></a></li>
		  <!-- HOME BUTTON HACK -->
 
		  <?php foreach ($this->getStoreCategories(10) as $_category):?>
				<?php echo $this->drawItem($_category) ?>
		  <?php endforeach ?>
		  </ul>
	 </div>
	 <?php echo $this->getChildHtml('topLeftLinks') ?>
</div>

Add Home Link To The Top Links Bar

<?php $_links = $this->getLinks(); ?>
<?php if(count($_links)>0): ?>
	 <div>
		  <ul<?php if($this->getName()): ?>):?> id="<?php echo $this->getName() ?>"<?php endif;?>>
		 
		  <!-- HOME BUTTON HACK -->
		  <li class="first"><a href="<?php echo $this->getUrl('')?>"><?php echo $this->__('Home') ?></a></li>
		  <!-- HOME BUTTON HACK -->
		 
				<?php foreach($_links as $_link): ?>
					 <li <?php if($_link->getIsLast()): ?> class="last"<?php endif; ?><?php echo $_link->getLiParams() ?>><?php echo $_link->getBeforeText() ?><a href="<?php echo $_link->getUrl() ?>" title="<?php echo $_link->getTitle() ?>" <?php echo $_link->getAParams() ?>><?php echo $_link->getLabel() ?></a><?php echo $_link->getAfterText() ?></li>
				<?php endforeach; ?>
		  </ul>
	</div>
<?php endif; ?>

Step One: Add .phtml to extension.txt in your Application Data

Step Two: Add .phtml to the extension.txt configuration file

Step Three: Add PHTML to MMDocumentTypes.xml

<documenttype id="PHP_MySQL" servermodel="PHP MySQL" 
internaltype="Dynamic"
winfileextension="php,php3,php4,php5,phtml"

macfileextension="php,php3,php4,php5,phtml" file="Default.php" 
writebyteordermark="false">;
</documenttype>