The foundation of the World Wide Web is hyperlinks. It’s how we get from here to there. Your job is to design a page so that all the links are unmistakable.
The most common way to make text links look clickable is to underline them. By the same token, don’t underline text that is not a link.
Links can skip the underline if they otherwise look clickable. For example, they can differ in color from static text. They can be styled like a button. Or they can be part of an otherwise obvious collection of navigation items.
Creating Usable Links and Buttons by Andrew Maier