Rails 3 generate model

I have done it before with an earlier version of rails eg :


but I am not sure of the command in Rails 3, and the 'require'
statements to ensure I won't get any 'no such file errors'.

There is plenty of documentation on how to create a generator but not
the more basic step of how to run the existing ones,

I don't know exactly how generators have changed but I'm curious - why
would you want your app to be running generators on itself at
runtime ?