In Magento store some times we are required to display best selling products on store’s home page or some other places. To do so we will perform the same as :

first of all we have to create a file in the path  app/code/local/Mage/Catalog/Block/Product/Bestseller.php with the following code in it :

class Mage_Catalog_Block_Product_Bestseller extends Mage_Catalog_Block_Product_Abstract{
    public function __construct(){
        parent::__construct();
        $storeId = Mage::app()->getStore()->getId();
        $products = Mage::getResourceModel('reports/product_collection')
            ->addOrderedQty()
            ->addAttributeToSelect('*')
            ->addAttributeToSelect(array('name', 'price', 'small_image'))
            ->setStoreId($storeId)
            ->addStoreFilter($storeId)
            ->setOrder('ordered_qty', 'desc'); // most best sellers on top
        Mage::getSingleton('catalog/product_status')->addVisibleFilterToCollection($products);
        Mage::getSingleton('catalog/product_visibility')->addVisibleInCatalogFilterToCollection($products);
 
        $products->setPageSize(3)->setCurPage(1);
        $this->setProductCollection($products);
    }
}

Secondly,  Create another file in this path app/design/frontend/default/YourTheme/template/catalog/product/bestseller.phtml with the following code in it. The below code will fetch the best selling products on the page but we have to call this code in a block. 

<?php if (($_products = $this->getProductCollection()) && $_products->getSize()): ?>
<div class="page-title">
    <h2><?php echo $this->__('Best Seller Products') ?></h2>
</div>
<?php $_collectionSize = count($_products->getItems()) ?>
<table class="products-grid" id="products-grid-table">
<?php $i=1; foreach ($_products->getItems() as $_product): ?>
    <?php if ($i%1!==0): ?>
    <tr>
    <?php endif ?>
        <td id="td_<?php echo $i;?>" <?php if($i%3==0 or $i==$_collectionSize){echo 'class="last"';} ?> >
        <?php contentBlock('top') ?>
        <div id="cont_<?php echo $i;?>">
            <h3 class="product-name"><a href="<?php echo $_product->getProductUrl() ?>" title="<?php echo $this->htmlEscape($_product->getName()) ?>"><?php echo $this->htmlEscape($_product->getName()) ?></a></h3>
            <a class="product-image" href="<?php echo $_product->getProductUrl() ?>" title="<?php echo $this->htmlEscape($this->getImageLabel($_product, 'small_image')) ?>">
                <img src="<?php echo $this->helper('catalog/image')->init($_product, 'small_image')->resize(122, 109); ?>" width="122" height="109" alt="<?php echo $this->htmlEscape($this->getImageLabel($_product, 'small_image')) ?>" title="<?php echo $this->htmlEscape($this->getImageLabel($_product, 'small_image')) ?>" />
            </a>
            <div class="a-center">                        
                <?php if($_product->getRatingSummary()): ?>
                    <?php echo $this->getReviewsSummaryHtml($_product, 'short') ?>
                <?php endif; ?>
                <?php echo $this->getPriceHtml($_product, true) ?>
                <?php if($_product->isSaleable()): ?>
                    <button class="button" onclick="setLocation('<?php echo $this->getAddToCartUrl($_product) ?>')"><span><span><span><?php echo $this->__('Add to Cart') ?></span></span></span></button>
                    <div class="clear"></div>
                <?php else: ?>
                    <p class="availability"><span class="out-of-stock"><?php echo $this->__('Out of stock') ?></span></p>
                    <div class="clear"></div>
                <?php endif; ?>
                <ul class="add-to-links">
                    <?php if ($this->helper('wishlist')->isAllow()) : ?>
                        <li><a href="<?php echo $this->helper('wishlist')->getAddUrl($_product) ?>"><?php echo $this->__('Add to Wishlist') ?></a></li>
                    <?php endif; ?>
                    <?php if($_compareUrl=$this->getAddToCompareUrl($_product)): ?>
                        <li class="last"><span class="separator">|</span> <a href="<?php echo $_compareUrl ?>"><?php echo $this->__('Add to Compare') ?></a></li>
                    <?php endif; ?>
                </ul>
                <?php if($_product->getevent_date()) {echo $_product->getevent_date();} ?>
            </div>
        </div>
    </td>
    <?php if ($i%3==0 or $i==$_collectionSize): ?>
   </tr>
    <?php endif ?>
  <?php $i++; endforeach; $kol = $_collectionSize; ?>
</table>
<?php endif; ?>

Now finally we have to call only the above code to display the best selling products on our store page this can be done as :

{{block type="catalog/product_bestseller" template="catalog/product/bestseller.phtml"}}