There are many different ways, just do a little research on finding do follow blogs. I also provide lists of do follow blog pages directly related to your business niche or keyphrase. This are the best type of links to build and have the best SEO value.
t Do not waste time in finding what is dofollow and nofollow.Google has content relevance factor that supercedes link juice factor most often as most seo's may have experienced. Comment on a blog that is relevent (keyword rich) to your content page (i mean deep linked site) this will help in categorizing crawler in correct niche and provide greater site visibility. If it is the PR for what you are looking blog with dofollow , better use article directories for backlinking as it is a known beneficial factor and quick too. This approach gave me 2 to 5 pr boost in 6 months with properly optimized articles for one of the site.
1. Search google for related blogs and forums. 2. Install SEOBook's toolbar for Firefox and turn on "hilite no-follow links". 3. For the blogs, look in the comments section. If everyone's links are hilited, then that is a nofollow blog. It is the same with forums. However, oftentimes forums are nofollow in the post, but dofollow for your signature. 4. Get involved only with those blogs and forums that pay back your participation with links.
I use a different plugin for Firefox called "NoDofollow", but it works the same; it highlights the links red or blue depending on whether they are dofollow or nofollow.
Why do you want to spam them? You want the blogs to leave your website there... not contribute... so why spam?
Use this Google Do follow Search : http://www.google.com/cse/home?cx=010363265520675485990:xjmxcyokkls
Some Site allows to list the dofollow blogs only. Search for the do-follow blog listing sites and submit your posts.