- Duplicate content.
-Doorway pages
-Keyword stuffing
-Link farming
-Hidden Text.

Dark cap SEO strategies, exemplified by spamdexing, involve controlling how internet searchers see the significance of a Web page in a way that is regularly conflicting with the web indexes' rules. Concealed content, shrouding, and blog remark spam are cases of dark cap SEO.

In search engine optimization terminology, black hat SEO refers to the use of aggressive SEO strategies, techniques and tactics that focus only on search engines and not a human audience, and usually does not obey search engines guidelines.

Black hat SEO refers to techniques and strategies used to get higher search rankings, and breaking search engine rules. Black hat SEO focuses on only search engines and not so much a human audience. Black hat SEO is typically used by those who are looking for a quick return on their site, rather than a long-term investment on their site. Some techniques used in black hat SEO include: keyword stuffing, link farming, hidden texts and links, and blog content spamming. Consequences of black hat SEO can possibly result in your site being banned from a search engine and de-indexed as a penalization for using unethical techniques.

These are black hat SEO technique
Unrelated Keyword
Duplicate content
Spam blog

-Keyword Stuffing
-Doorway pages
-Link farming
-Hidden text

What Is Black Hat SEO?
What Is Black Hat SEO? A Definition

Black hat SEO refers to a set of practices that are used to increases a site or page's rank in search engines through means that violate the search engines' terms of service. The term "black hat" originated in Western movies to distinguish the "bad guys" from the "good guys," who wore white hats (see white hat SEO). Recently, it's used more commonly to describe computer hackers, virus creators, and those who perform unethical actions with computers.

The following SEO tactics are considered black hat and should not be exercised at all if you want to stay above board with Google and other search engines:

Content Automation
Doorway Pages
Hidden Text or Links
Keyword Stuffing
Reporting a Competitor (or Negative SEO)
Sneaky Redirects
Cloaking
Link Schemes
Guest Posting Networks
Link Manipulation (including buying links)
Article Spinning
Link Farms, Link Wheels or Link Networks
Rich Snippet Markup Spam
Automated Queries to Google
Creating pages, subdomains, or domains with duplicate content
Pages with malicious behavior, such as phishing, viruses, trojans, and other malware

Black hat SEO refers to a set of practices that are used to increases a site or page's rank in search engines through means that violate the search engines' terms of service.

Let see, we can classified them like this:
- Black Hat SEO - guys who will do anything to gain traffic (such as spamming/duplicating) in short time. The good thing is they can get considerable amount of traffic in short term, but in the long term it is not stable. Just like the recent google penguin updates, it really messes Black Hat up.

- White Hat SEO - 'good guys' who focus on doing good and variety of content, contributing organic/natural traffic rate.

- Grey Hat SEO - guys who do both White Hat and Black Hat, but some say that they are Black Hat disguised as White Hat.

A Definition. Black hat SEO refers to a set of practices that are used to increases a site or page's rank in search engines through means that violate the search engines' terms of service. ... Tactics and techniques that qualify as Black Hat SEO.

30 Black Hat SEO Techniques You Can Use Ethically

search these and you will find good article about that

Black Hat SEO Follow the guide Line Of search engine.

Hidden Text
Doorway Pages
Keyword Stuffing
Link Farming
Cloaking

Black Hat SEO techniques are the techniques which do not follow the guidelines of search engines. The website which implements Black Hat SEO techniques gets banned or penalized by search engine. Some of its techniques are:

keyword studding
duplicate content
cloaking
doorway pages
negative SEO
hidden text or urls etc

here are some technique which is used in blavk hat SEO.

Unrelated Keywords.
Keyword Stacking and Keyword Stuffing
Tiny Text, Hidden Text, and Hidden Links
Cloaking.
Doorway Pages or Gateway Pages.

-Duplicate content
-Doorway pages or Gateway pages
-Hidden text
-Keyword stuffing
-Cloaking