Just create the steps using simple boxes then mirror them over for the other side. (fig.25)
fig.25
Here it is after a little more work, sorry I didn't go into it in more detail, but a lot of it is just simple boxes, it also depends what variation you are trying to model, not all of them are the same. (fig.26)
fig.26
Now for the handrails, an easy way of doing them is to create a spline in the shape of the hand rail and loft it with a small circle, in the picture below we can see the spline and circle. (fig.27)
fig.27
When you go to loft the object make sure to go into the "Skin Parameters" rollout and change the shape steps and path steps to 0. After that is done go ahead and convert it to an editable mesh. (fig.28)
