One simple algorithm for early retirement

A. Do you want to retire?

Yes - Go to B                      
No - Stop reading (Some people are lucky enough to to something they like, so you can see the necessity to retire if you have a better alternative. Of course, it is much rewarding to go to your actual work as volunteer knowing that your bank account is big enough so you do not need to work another day of your life if you do not need or want.)

B. When do you want to retire?

At the retirement age, as everybody else I know - Stop reading.
Before the retirement age - If this is your wish, my friend. You need to start saving. And more than that, you need to know how much you need to save, therefore you need to calculate your retirement expenses and to know how to provide your retirement income. Go to C.

C.  What will be the estimate cost when you will retire?

You are rich - Stop reading.
You know why you want to retire and when, now you need to know what your expenses will be and how to cover them -  You need a decent plan on how to generate wealth and passive income (because of ageing), and how to overestimate a bit your needed income (because inflation, global crisis and stuff). Go to D.

D. The plan

Once you are here, you have your plan, and you can divide the years until your retirement to find how much you need to save yearly. Then you need to start saving, record everything, reach the retirement date, retire and make a good book about this. Do not forget to sent me the book. I promise i will read it.