backlink fully

Yes it must be dofollow

make use of various various online tools available such as woorank.com, seositecheckup.com/ to find out missing basic elements of your website. Also as other mentioned there is three types of seo-
1. on page seo
2. on site seo
3. off site seo.
Off site seo majorly include backlinks to your website and plays a good role in ranking your website.

Study the content and backlinks of high ranking websites that offer your products or services.

Good Luck

Seo Stands for Search engine optimization.SEO method is more effective and useful way for build backlink of website.

SEO is a best technique for increase the visibility of the website. SEO has two types of strategy like on page seo and off page seo.

Seo is classified into on page and off page.
some of the SEO methods are
blog commenting
Directory Submission
Blog Submission
Article Submission
Forum Posting
social bookmarking
infographics