Using JTable is a great, and the correct way to manipulate data tables in Joomla, but having some helper functions makes it much easier. 

<code php>
function InsertTable($tablename, $cols, $values) {
        $db = JFactory::getDbo();
        $query = $db->getQuery(true);
        
        $query
        ->insert($db->quoteName('#__'.$tablename))
        ->columns($db->quoteName($cols))
        ->values(implode(',', $values));

        $db->setQuery($query);
        $this->dmesg(2,2,"Query",$query->dump());
        try {
            $db->execute();
        } catch (Exception $e) {
            // call failed, do something here. 
        }

}
    
function UpdateTable($tablename, $values, $Where) {
        $db = JFactory::getDbo();
        $query = $db->getQuery(true);
        
        $query->update($db->quoteName('#__'.$tablename))->set($values)->where($Where);
        
        $db->setQuery($query);
        try {
            $db->execute();
        } catch (Exception $e) {
            // Failed, do something here. 
        }
        
}
</code>

InsertTable takes the table name (without the prefix), an string of comma separated column names and an array of values. 
UpdateTable takes the table name (without the prefix), a string of updates (column='value',) and a where clause as a string.