How effective is backlinks?

One of the way to practice SEO for our blog to generate traffic is backlinks. But I would like to ask our effective it is and how to do it right so that we won't be penalize by Google?

Backlinks is very important factor in determining the ranking of a site. In fact, backlinks is like recommendation that your site is okay from third party. Not all backlinks is valuable as such. Backlinks from spammy sites can cause more harm than good.

Backlinks is very important factor in determining the ranking of a site. In fact, backlinks is like recommendation that your site is okay from third party. Not all backlinks is valuable as such. Backlinks from spammy sites can cause more harm than good.

Backlinks will become effective only when they come from sites that are ranked higher than yours, when backlinks are do follow, and when the backlinks come from similar niche website