Consider your needs. If you live in a studio or small loft a staircase that doubles as a shelf or dresser may be ideal. On the other hand, if you want a decorative design that is not the only option for reaching the next floor, a spiral stair case may work. These stairs are also ideal in odd shaped homes like those built in grain silos, but they are not permitted in all areas or may have specific requirements. So, check your local building codes. Steel also works well for purely functional pieces in heavy traffic areas like offices or malls but they should be well-textured or people may slip.
Measure your space. In particular, measure the hole opening to the next level, the distance from the floor to the ceiling and the amount of available space around the stairs. Some stairs take up a great deal of space so you need to make sure people can get around them. Also keep in mind how the stairs will be set up. Floating stairs are bolted into the walls and do not take up much space but some artistic stairs are held in place by a complicated array of metal wires, which look attractive but make the surrounding space unusable.
Collect images of inspiring stairs. Do not just stick with steel steps, look at wooden or industrial strength glass ones as well since a talented welder can create a "carved" effect with metal. You should also look at general design images or other things that interest you. For example, an image of waves may inspire you to create a uniquely curved stair, as if waves are carrying you upward to the next floor.
Measure and write down the distance that is most comfortable for you to step up or down. This can vary depending on your age, height or even weight. A simple way to do it is to keep a measuring tape on you and measure steps that feel comfortable to you as you go on with your day. You may also want to measure steps that feel uncomfortable to you and write down their measurements as well in case your exact measurements are not doable. This way you can tell exactly how much space you can give before becoming uncomfortable. You should also measure the depth of steps. Even on spiral staircases the depth of each step should be enough for your entire foot and an extra inch or two in case you slip to give yourself space to catch yourself.
Create textural elements such as bumps, ridges or slots along the edge of each step. Steel can be slippery, particularly when wet. Use the effects to slow down movement and reduce the likelihood of slipping.
Draw an image of a staircase incorporating all of these aspects. Have a drafts person, engineer or architect examine it to make sure it can be created in steel and still be safe for use.