What are some common Black Hat SEO techniques?

When it comes to black hat SEO tactics, these refer to deceptive or manipulative practices that go against search engine guidelines and aim to artificially inflate a site's rankings. Some of the most common ones include:

Keyword stuffing by excessively repeating keywords in content or meta tags way beyond what's natural or relevant. Search engines view this as spam.

Cloaking, which means delivering different content to search engine crawlers than what human users see. It's a way to try to game the systems.

Link schemes like participating in link buying, link farms, or excessive link exchanges solely for the purpose of boosting rankings rather than citing quality sources.

Using automated techniques to generate spun or low-quality content at scale with the sole intent of manipulating search results rather than providing value.

Creating "doorway pages" - basic pages stuffed with keywords just to try and funnel traffic to a different destination site.

Implementing malicious redirects that send users and crawlers to unintended places, often for spam purposes.

Things like negative SEO attacks, and trying to undermine a competitor's rankings by hacking them or blasting them with spam links.

Hiding text or links using tactics like tiny/invisible fonts or white text on white backgrounds in an attempt to deceive search crawlers.

Automated blog comment spam and forum spam to drop inbound links on other sites.

And misusing structured data markup like schema code in misleading or deceptive ways.

Essentially, any tactic that is artificial, deceptive, or prioritizes manipulating rankings over the user experience - is considered a black hat and a violation. Search engines have gotten much better at detecting these and imposing penalties accordingly.

The sustainable approach is to focus on ethical, white hat practices like publishing high-quality content, earning authoritative backlinks, optimizing for performance and UX, etc.