They didn't mention the real trick in the advice section: Don't have kids.
The real trick is living way below your means. The main cost factors for most people are shelter, transportation and food. If you manage to lower these three recurring expenses considerably, you can retire within 5-10 years (even if you don`t make a six figure income).
Early retirement means that you are financially independent, which is defined as the state of having sufficient personal wealth to live, without having to work actively for basic necessities.