Do not skip the warm-up, and consider using resistance bands to assist on higher-volume sets if your form begins to break down.
While the is legendary, it is not for absolute beginners. The strain on the elbow tendons (specifically the medial epicondyle, or "golfer's elbow") is significant. In 2011, many copycats posted injury logs on forums due to jumping into L-sit pull-ups too quickly. bar family 2011 workout
Keeping the core tight, lower your chest to the bar and press back up to full elbow extension. Do not skip the warm-up, and consider using