some black hat techniques are

Cookie Stuffing or Cookie Dropping
Social Networking Spam
URL Hijacking
Domain Squatting
Link Farms
Referrer Spam
Spam Ping
Trackback Spam
Blog Spam

These are black hat SEO techniques:
Unrelated Keyword
Duplicate content
Spam blog

Let me explain about black hat techniques.Spamming technique is otherwise known as blackhat methods..These are the following techniques used now a days..
KEYWORD STUFFING,
SPAM COMMENTING,
INVISIBLE TEXTS ,
ARTICLE SPINNING,
DUPLICATE CONTENT,
CLOAKING,
but if u use these techniques they are usually detected sooner or later and your page rank may get lower also be banned..Better advise is use greyhat technique..

Top black hat seo techniques are
.Hidden Content
.Cloaking
.Doorway pages
.Meta keyword stuffing
.Link Farming

Keyword Stuffing
Duplicate Content
Cloaking
Doorway pages
Paid links

- Keyword Stuffing,
- Cloaking,
- Doorway pages,
- Paid links,
- Hidden text,
- Paid links.

Some of the black hat techniques:
Duplicate content
Negative Seo
cloaking

TOP 5 BLACK HAT SEO TECHNIQUES
1 Hidden Content.
Top of our list of black hat SEO techniques is hidden content.
2 Meta Keyword Stuffing.
There are two Meta tags that are generally used to inform search engines of the content on the page.
3 Meta Keywords.
4 Doorway or Gateway Pages.
5 Link Farming.

Keyword Stuffing, Duplicate Content negative seo.