Search engines do not see all web links the same. In fact, it is possible for a web master to request that a search engine NOT follow certain links to keep SEO value from "leaking" from a website. Some websites, blogs, and other web tools may allow you to link as a professional without providing you with search engine credibility.
Search engines use special properties within link tags to determine whether or not they should spider the link and follow it to the next page. The property may be set to "dofollow" or "nofollow". The search engine then knows what it should do when it arrives at a link.
Professionals work diligently to promote their websites to search engines. What pros may not know is that a site they believe is providing great SEO benefits may simply be using their content for their own purposes without providing linkthrough credibility.
Many online professional services like ProSPOTLIGHT, and others offer the ability to make posts and submit content with "dofollow" status. Any time a pro links from that service to another website, they receive the SEO benefit.
The key is to find websites that are known for their "dofollow" practices.