Starting a cult takes some planning and preparation. Firstly you have to study people. Take a course in sociology or psychology to learn about what drives people.
Secondly, you need to study the fine art of fortune telling. Combined with the psychology and/or sociology skills, you will be able to impress people with your "powers" and "wisdom".
Now is the time to consult a fashion designer. Every cult has its own unique dress. Perhaps you like the clean lines of a basic long tunic, or maybe you incorporate your favorite colors into a new fashion design. The choice is yours! Just be sure your personal outfit is formal and impressive.
While you are charming folks and creating a following for yourself, don't forget to brush up on your basic theology. As time passes, you must solidify your cult's beliefs. You must incorporate wise sayings into your daily meetings with potential followers. Write them on business cards and pass them out, leave them everywhere.
Now it is time to think about location. Seek out a meeting place. It could be an old warehouse, a barn, an airport landing strip, somewhere that will hold the amount of people you expect to show up. Account for friends and guests as well. The more the merrier!
Always collect money. Use it to buy a large plot of land. Perhaps write for grants, or get charitable donations. Also sending people out into the community doing good works keeps the police off your back. They'll turn a blind eye on the barbed wire fencing you put up around your new location.
Once your fencing is in place and your locale is secure, let only the "chosen ones" enter it, lock the gate, and throw away the key. Select them based on physical appearance, entertainment value, and talents. You'll need carpenters, plumbers, mechanics, secretaries, and wenches (if male).
Do what you can to make it as self-sustaining as possible. The longer you remain peaceful, and stay out of contact with the world, the longer you can enjoy the benefits of lording over your subjects.
The most important thing at this stage is to make yourself inaccessible to your people. Hide in your rooms. Tell them you are communing with the spirits and they are angry. You are battling for their lives, and it has made you very tired, or irritable. The more mystery there is around your persona, the more people will believe you. As the generations pass, fewer will remain who actually have looked upon your face and you will be free to have whatever desires your wrinkly old self craves; firstborn, palm leaves waved over you, bellydancers, or wine.
Most importantly, prepare the people for mass suicide when you die. You don't want the truths of your "business" to come out after your death. This is your party and it must end when you do!