There's a German tool for doing it automatically, but the good ol' manual way still gives the best control over getting exactly what you want. This assumes you know the basics of map making...

1. Create the guiding path of the staircase. This is done with the help of 2 cylinders (or bevels if prefered).



2. Use patchmeshes to get the angles for each step. Over here I'm using 22.5 (well 23 actually) degree increment. The angle you use depends on the length you want your staircase to be and the height you want it to reach.



3. Make the steps by using the intersections between the meshes as guides. You can use either brushwork, patches or a combination of both to do this. Use smaller grids depending on how accurate you want it to be - I'm using Grid1 here. If you're using brushes then have caulk applied to them.



4. Push each step higher than the previous to make them into actual steps. Here we've got 4 steps which make up 90 degrees. Since 4 steps in this tutorial make up 90 degrees we can just clone it if we want a 180/270/360 degree spiral. Group it and set as detail (if you're using brushes).







5. Texture all visible faces as usual, delete the meshes.