How to design the user table in database?

I want to develop a server side of an app that holds users. Of course I need a table in database holding the user information. At first I may write

class User(models.Model): # using django models
    userid = ...
    password = ...

which gives me a database table containing userid and password.

However, I might want to add some attributes (maybe Credit, Birthday...so on) to each user in the future. I just can't think up all of them right now. And I can't know what attributes I would really need in the future.

How can I deal with it?