Why important to tag blog published post.

What some people's do wrong with tags? May be you are also

1. People use lot's of tags in blog post, so generally tag is consider one webpage, so whenever google bot crawl your site, it will pass some juicy rank to that tag, so by adding lot's of tags, you are just wasting your juicyrank/pagerank to that tag.

2. Tags should be noindex i.e. your site tags should not be index on Google, because it is automatically generated by your blog, and it is low quality, because same post title and description appear in different tags. Look out labnol blog, it is panalize by Google panda, because his tags was index on Google SERP, and Google assume, the tags pages are generally low quality, it is good for users, but in certain limitation. By adding lot's of tags, looks spam.

I would suggest, use only few tags like one or two per post, and try to use same tag on other blog post. And one last think, by adding tags, you will not get higher ranking, yes some of getting higher ranking for tags, because most of post, point to that tags, and pass more juicyrank to that tags, and hence it is ranking, but when Google Panda rolling out, you will lost your position in Google SERP.Hope it helps :)  

Rajesh internal backlinking is as important as back linking. Check out this article for information > http://teachmate.org/internal-links-how-to-use-them-to-boost-search-engine-rankings/