In web development, separating CSS into external files provides multiple benefits. External CSS files can be reused across different web pages, promoting consistency in design and making maintenance easier. Additionally, it allows developers to focus on writing clean HTML code without cluttering it with styling details. Here's a step-by-step guide to creating and linking external CSS files:

1. Create a new file with a .css extension. For example, style.css.
2. Open the file in a text editor and start writing your CSS rules.
3. In your HTML file, add the link tag between the head tags, and set the 'href' attribute to the path or URL of your CSS file. For example:

<link rel='stylesheet' href='path/to/style.css'>

It is important to ensure that the path specified in the 'href' attribute accurately points to the location of your CSS file. Otherwise, the styles won't be applied. If you are working locally, make sure the CSS file is in the same directory as your HTML file or provide the relative path.

Once you have linked the external CSS file, any styles defined in the file will be applied to the HTML elements as specified. Remember to save both the HTML and CSS files and refresh your web page to see the changes.

Best Practices for Structuring CSS Files:

1. Use a consistent naming convention for classes and IDs to keep your code organized and maintainable.
2. Group related styles together to make it easier to find and modify them later.
3. Consider using tools like SASS or LESS to enhance the capabilities of CSS and improve code organization.

By linking external CSS files, you can streamline the development process and maintain consistent styles across your website. Happy styling!