There are mainly three SEO Techniques. They are:

1. White Hat SEO
2. Grey Hat SEO
3. Black Hat SEO These are the most famous SEO Techniques. In white hat SEO are the ethical and legitimate ways are used to rank a site it takes a lot of effort and time but both effort and time is worth it. When it comes to black hat SEO it is the complete ethical way by which u can come on top easily but once google finds out u have not used right ways it drops your position. In the grey hat SEO it is the mixture of white hat and black hat and in this it tough for the goggle judge that few mal practices have taken place. The most working black hat technique is the backlinks.