Your chickens' roosting area should serve to protect them, not increase their vulnerability. Roosting on the steps of your home puts your chickens at risk from predators; roosting even on the chicken coop stoop is risky. Your home's steps, meanwhile, are a highly inconvenient roosting place, because everyone attempting to walk on the stairs will risk stepping on if not tripping over your chickens.
Chickens will choose nesting locations in which they feel safe and comfortable. In a controlled environment such as a chicken coop, you can basically force your chickens to select a specific location to nest in -- such as inside a nesting box. Chickens who are left to roam freely will roost wherever they please. If your hens live outside at least part of the time, they have the ability to nest wherever they choose. Your idea of a good place to nest may be quite different from your chickens'.
The Chicken Coop
The easiest way to prevent your chickens from nesting on your steps at night is to make sure they do not have the option of doing so. Keeping your chickens in a coop will prevent them from nesting anywhere outside of the coop. Provide your chickens with secure, roomy and clean nesting boxes within the coop. Keeping your chicken in a locked coop will keep them safe from predators and ensure they roost only in areas where you want them to be.
Free Range Roosting
If your chickens roam freely during the day, it will take some work to teach them to roost where you want them to. If you want your chickens to roost inside a coop, you will need to physically place them in the coop or lure them into the coop with feed during the late afternoon or early evening until it becomes a habit for them to go into the coop by nightfall. If you want them to roost anywhere besides on your steps, you need to provide them with a comfortable and safe alternative location. You can try placing nesting boxes near the steps or in an area your chickens like to nest in, then encourage the chickens to choose this area instead.
Make your steps uncomfortable for your chickens to roost on. Keep the area around your steps brightly lit. Fence off the area directly around the steps to prevent your chickens from easily walking onto the steps. Keep the steps clear of plants, hay, straw and any other nesting-type materials. Remove any bedding or materials from the steps that would make them a comfortable area for chickens to nest. Place the bedding your chickens prefer into a proper nesting location and place your chickens in the same location.