I use both of them. But I give priority to dofollow. Because they are important for search engines. I think nofollow link only can help your website increase traffic. it can not a backlink to Google evaluation. Just give importance to do-follow but not forget or leave no-follow links every link have its own importance. For detecting the spam you should build no-follow and do-follow links. This is the natural way link building for a website. Having both.
When creating backlinks, just follow the basic steps like:
(1) Blog commenting on dofollow blogs
(2) forum posting with signature
(3) article submissions
(4) social bookmarking
(5) Post Guest post in blogs
(6) Conduct Keyword Research
(7) Link Wheel
(8) Web 2.0
(9) Blog Commenting
(10) Forum Commenting
(11) Ads Posting through Classifieds
(12) Press Release
(13) Slides Sharing
(14) Video Marketing
(15) Article Marketing
(16) Guest Posting