Black hat SEO has a negative reputation, and rightly so: It's a shady set of deceptive practices that degrade the user experience and are adopted mostly to make a quick buck. To keep a business legitimate and afloat on the Web, avoid black hat SEO techniques and embrace white hat SEO techniques.
Unrelated Keywords, Keyword Stacking and Keyword Stuffing, Cloaking, Doorway Pages or Gateway Pages, Duplicate Content or Mirror Site, Cybersquatting or Domain Squatting...
There are lots of black hat techniques in seo like duplicate content, doorway pages, traffic exchange, keywords repetition, cloaking and more activity are present in the seo but i suggest you don't apply for website promotion, it should be harmful for your website.
If you take short cut rout then you can reach to your destination but there are more risk. So which technique is legal only that technique only be adapted for promotion and increasing the traffic of your website. So black hat technique like using duplicate content ,traffic exchange , key exchange and may more these type of technique should not be used for increasing the traffic of your website.
Here are some techniques whose used in Black hat SEO, But many SEO expert say that more than 20 techniques in Black hat SEO. Cloaking:- It is hide the heavy Flash animation from google. Paid links :- Many of them display links to those who donate. Scraping :- Create mirrors for popular sites. Rogue bots :-Spider websites aware of broken links and other issues. Doorway pages :- Doorway pages are worthless craps during landing pages.
The following are some common blackhat SEO tactics:
Keyword Stuffing - Repeat the same keywords too many times
Making Text Same Color as Background
Tiny Text - Make the keyword so small that no one can notice it
Cloaking - Present one set of pages to the search engine and another set of pages to the visitor
Doorway Pages - Stuffing the page with keyword to achieve a higher ranking and automatically redirect the visitor to a different page.
Page Swapping - Changing the page content after getting indexed and ranked
Duplicate Content - Copy someone else's content and put it on your site
Spam Blogs - Create spam blogs to generate backlinks
There are lot of black hat techniques and more are developing everyday, it is just all about how do you manage your techniques to be not known to search engines and still you getting your websites profited.
Although, people do not mind using it but they do know that the bad time they could have using it.
There are numerous types, unless you post the one you want. Some people has made bots for automatic followers on social media sites. Some of them were automatic comments, articles posters. My suggestion is never try such things in life if you are a serious developer.
Keyword Stacking and Keyword Stuffing
Tiny Text, Hidden Text, and Hidden Links
Doorway Pages or Gateway Pages
Bait-and-Switch or Page Swapping
Duplicate Content or Mirror Site
Spam Blogs or Splogs
Blog Spam or Comment Spam
Social Networking Spam
Spam Ping or Sping or Pingback Spam
Cookie Stuffing or Cookie Dropping
Typosquatting or URL Hijacking
Black hat SEO has a negative reputation please don't ever use this trick this if google know about your site and it realise that you are doing you site's SEO in black hat way than google will band your site it is totally illegal.