Step 1. Consider a Free Web Hosting Service
Some companies will let you set up a Web site free, gratis, and for nothing. These free hosting services make their money from the advertising they graft onto your pages.
Now, you can tell from this very page that I'm not an enemy of advertising (so long as it's useful to the reader). With any luck, the ads on this page mostly tell you about free Web hosting, which makes it easy to check them out.
I've never used free Web hosting, but I've noticed that such pages tend to be slow to load, and the companies offering them sometimes vanish on short notice. Still, they're a no-cost way to get your feet wet.
Tip: You can always move your content to a new hosting service if you get tired of your old one, so decisions at this point aren't going to bind you.