Use your browser's Developer Tools (F12) to inspect elements: right-click the target element, select "Inspect", then right-click the HTML and choose "Copy → Copy selector". Test selectors using Ctrl+F in the Elements panel. For a complete walkthrough, see our Finding CSS Selectors with Browser Developer Tools section above.

ID selectors (#id) are fastest, followed by class selectors (.class), then attribute selectors ([attr=value]), element selectors (div, span), and complex selectors. Use IDs when available, combine element and class selectors, and avoid overly complex selectors for better performance.

CSS selectors are more concise and readable with better performance, but limited to forward navigation and cannot select by text content. XPath is more powerful and flexible, can navigate in all directions, select by text content, and supports complex expressions, but has more verbose syntax. For a detailed comparison table and when to use each, see the CSS Selectors vs XPath section above.