Sort Omeka Items alphabetically by title by default.

sort_items_by_title.php

<?php

function custom_item_browse_sql($select, $params) {

    $sortField = 'Dublin Core,Title'; // 'Element Set Name, Element Name'
    $sortDir = 'ASC'; //ASC or DESC

    if (!isset($params['sort_field'])) {
        $select->reset('order');
        get_db()->getTable('Item')->applySorting($select, $sortField, $sortDir);
    }

}

add_plugin_hook('item_browse_sql', 'custom_item_browse_sql');