Listening to youtube comments is like slamming yourslef in the forehead with a sledgehammer - you get a headache, don't learn anything and end up stupider.
http://www.youtube.com/watch?v=Ls9EygRn_3c - Oli Thompson deadlifting, former Britain's strongest man, right up until he tears his bicep this is a rather good video. Focus on head up, spine stays in neutral, drive with the legs then once they go straight lean back and straighten up.