I want to add field sort order in admin grid and in frontend part (sort by). I make module "news" and want to sort my news by title.

Please guide me how to do it

<code>
    protected function _prepareCollection()
    {
        $collection = Mage::getModel('mdnews/news')->getCollection();
        $this->setCollection($collection);
        return parent::_prepareCollection();
    }

    protected function _prepareColumns()
    {

        $helper = Mage::helper('mdnews');

        $this->addColumn('news_id', array(
            'header' => $helper->__('News ID'),
            'index' => 'news_id',
            'width' => '100px',
        ));

        $this->addColumn('title', array(
            'header' => $helper->__('Title'),
            'index' => 'title',
            'type' => 'text',
        ));

        $this->addColumn('category', array(
            'header' => $helper->__('Category'),
            'index' => 'category_id',
            'options' => $helper->getCategoriesList(),
            'type'  => 'options',
            'width' => '150px',
        ));

        $this->addColumn('created', array(
            'header' => $helper->__('Created'),
            'index' => 'created',
            'type' => 'date',
        ));

        return parent::_prepareColumns();
    }
</code>