Yes focus on making do follow links which 'll help you to reach in googd SERP From blog commenting, forum posting, articles, social book marking etc.......but dnt forget from guest blogs which great values now a days
Links to authorities and to pass along a link juice. Stronger and more authoritative the page is a link, it helps with SEO backlinks. For example, a blog post a blog authoritative links to your site will help more than just a directory listing of a website directory of small class page buried deep in the site indefinitely.
for the no follow you 'll get traffic from that link but do follow 'll help as a link juice and ranking as well
Do-follow backlinks pass some link juice to your links, no-follow backlinks do pass some backlinks just not as much as do-follow
Both dofollow and nofollow links gives traffic to your site. But in the case of dofollow ,at the time of Google crawl it will also crawl the dofollow links available in the page by visiting it.It will also consider for ranking the website. In the case of nofollow links it won't be crawled while crawling the site.Its just for a referrance .So better you find dofollow blogs and start commenting to get backlinks .My blog moretricks.com has acheived a page rank of 2 in the last Google page rank update.My blog is also made as dofollow by me.
edu and gov backlinks are valuable links ,but getting backlinks from those sites is difficult and also one thing is nofollow links wont juice up your rank
Here's a good post on using nofollow noindex tags and when to use them: http://www.bloghighlight.com/seo-strategy-for-noindex-and-nofollow/
Do follow and no follow links give traffic to your site. Do follow links have more weight because they help boost your website's ranking.
do follow is by default, no follow is for those site you dont want them in index.. Its good to opt out some pages (likk juice will pass from root domain to important pages only).
Both dofollow and nofollow have their own impact. Dofollow passes the juices and increase your position in serps and nofollow have importance in Yahoo .
Do-Follow is that from where you get back link and link juice will also be transfer but in No-Follow you only get back link link juice will not transfer.