The stair is considered by many people to be one of the, if not the most, versatile blocks in Minecraft. They can completely change the look and feel of a build and increase its quality. In this post, I will highlight just a few of the options you have for using them.
The first and most obvious use of stairs is to use them as an actual staircase. This can be a spiral staircase, a grand staircase in a mansion, or just a plain old set of steps.
Another way to use stairs in you build is to create indents or "chinks" in a wall. These can be used to create texture or just let a small amount of light in.
Next, you can use stairs as the base of a pillar or a wall. This makes a build look more realistic, as large stone pillars sometimes need side supports, and helps a build to flow more into the landscape.
You can also use stairs to create a somewhat smooth archway. Making an arch just out of normal blocks looks too cuboid. Adding stairs helps make it a little better.
Finally, stairs can be used to create more interesting and intricate windows. These type of windows look the best in castle-like buildings and stone fortresses.
Here are all of the different uses of stairs combined into one wall, save a normal staircase. The only blocks I used were cobblestone, cobblestone stairs, and smooth stone (to make it look not as monochromatic).
However, keep in mind that these are not all of the uses for stairs in Minecraft and you can expand greatly on all of these tactics for using stairs. I merely went over a few of the basics and some practical uses of them. Whenever your build looks bland or uninteresting, consider adding a few stair blocks to change add texture or more support. If you've got other ideas, let us know in the comments, or post some pictures to the corkboard.