Form post to DB with safe inputs

[eluser]RaZoR LeGaCy[/eluser]
I am unsure as how to properly make form variables safe to input into databases

How can I make this data safe to insert into the DB

Code:

$data = array(
               'rid' => ''.$_POST['rid'].'' ,
               'cat' => ''.$_POST['cat'].'' ,
               'c_author' => ''.$_POST['c_author'].'' ,
               'comment' => ''.$_POST['comment'].'' ,
               'c_score' => ''.$_POST['c_score'].'' ,
               'time' => ''.$_POST['time'].'' ,
               'ip' => ''.$_POST['ip'].''
            );

$this->db->insert('hellhorror_reviews_comments', $data);


redirect('movies/comments/'.$_POST['rid'].'/');

Thanx everyone,
I always get confused with this part.