Stairs, along with horses, would make it onto many artists list of things they hate to draw. In my experience drawing comics, I've had to draw stairs now and again and I've learned a few tricks worth sharing.
Now, I’m a firm believer in drawing from observation. Looking at the world thoughtfully and studying it. When I’m drawing a room and I can “see” the stairs go up into the distance and “see” how large each step should be, just by feel, that is somewhat inaccurate, but, to me, the ideal way of doing it. But nonetheless, there is a method I’ve found that helps me draw them.
The average ceiling is 9-9.5 feet. That means the stairs will have to travel up 9.5 feet PLUS the height of the floor/ceiling joists. Easy to forget that when drawing–to make the stairs go up above the ceiling by and extra foot.
Stairs go up/down at an angle of just under 45 degrees, let’s say 40 degrees. That means that they are longer than they are tall, by a little.
A good stair step height is 7” and the depth of a step is more like 9-10”. So notice that a stair step is similar to the size of a human head and the steps could fall around the points that the human head hits the human form. (This applies more to residential stairs; steps tend to be much deeper in public and outdoor spaces.) At 7-9 inches per step and a height of 10 feet, you are looking at 13-16 steps in a staircase. (This applies more to residential places; adjust as needed.)
Instead of trying to draw stairs, I recommend starting with a ramp. I like to model the ramp as coming off of a floor/ceiling joists area, with a rectangle above it and below it that represents the wall above it and below it (the space from floor to ceiling on each floor). From the floor/ceiling joists area, you can project a rectangular prism. This prism is the root of the model; the rectangles that represent each floor extend off of it at each end, perpendicular to it.
Notice the relationship between that "root" rectangular prism and the vertical rectangles of the door/wall sections. If it you get a feel of the ratio between them, it becomes even easier to draw and manipulate this shape in space by feel, like below.
Go ahead and try filling a page with this shape, turning it in space. Then, try fleshing it out more, with a room, a figure, and such.
Refining the ramp into stairs, minding the vanishing point and perspective rules... I'll leave that to you. I hope this model/idea helps you the next time you have to draw stairs!
Happy drawing!
-Ike