_initModel function for the frontend indexController

IndexController.php

<?php 
...

    public function _initModel($param = 'id')
    {
        $model = Mage::getModel('mdg_giftregistry/entity');
        $model->setStoreId($this->getRequest()->getParam('store', 0));

        if( $modelId = $this->getRequest()->getParam($param))
        {
            $model->load($modelId);
            if(!$model->getId())
            {
                Mage::throwException($this->__('There was a problem initializing the gift registry.'));
            }

        }
        return $model;
    }