Plasmid DNA isolation using alkaline lysis method

Hi, I’m new in the field of molecular biology; I want to do Plasmid DNA isolation using alkaline lysis method to obtain a large amount of DNA. I did it several time but unfortunately it didn’t work. On electrophoresis gel I obtain one band and sometimes nothing. But I want to observe the three forms: circular, linear, and supercoiled .
Did you know what my problem is? Could you give me a simplified and clear protocol