Seo techniques are a broad subject. However, we can classify them into two main categories. They are White Hat SEO and Black Hat Seo.

White Hat SEO contains the techniques that are appreciated by Search Engines. They are not harmful, they do not try to trick search engines.

Black Hat SEO contains harmful SEO practices and they try to trick search engines. They try to give you a rapid rise in the search results, however the results could be disaster for you when Google notices.

White Hat SEO Techniques

White Hat SEO techniques should meet the requirements below

It should be compatible with the search engine’s principles
No deception should be involved
The content which search engine indexes, should be the same with the content that users see
The satisfaction of users should be considered as well as search engines
Design and interface of the webpage should be good
The content on the website should be original

If you want an organic increase in the search results, you should follow White Hat SEO techniques.

Black Hat SEO Technique

Black Hat SEO Technique contains harmful activities which you can see below

Are not compatible with the principles of search engines
They try to deceive search engines
Redirecting users to a page which is different from the page in search results
Holding a version of a page to serve search engine bots and another version of page to serve humans. This technique is called Cloaking.
Keeping an invisible text on the page which has the same background colour with the page
Using excessive keywords in metatags or using irrelevant metatags. This is known as metatag stuffing.
Having very few content, which are full of keywords on the website instead of creating good content.
Having mirror websites to support the main website with nearly the same content but with different URLs.
Instead of creating an original website, copying a popular website.

Black Hat SEO could be very harmful for your website when it is noticed by Google. You will most probably be fined and in the worst scenario, your website will be banned. Thus, I recommend you to learn White Hat SEO techniques and use them. The necessary time to learn SEO techniques will depend on your commitment and skills. It could take six months, a year, two year etc. It depends on you.