Interesting discussion! I would love to start with dividing the 3<sup>rd</sup> party website in to different forms.
- 3<sup>rd</sup> party websites like Yelp.com and other Yellow pages websites
- 3<sup>rd</sup> party websites like trip adviser who allow limited niches to promote their services (niche related portal)
- 3<sup>rd</sup> part websites like SEOmoz who are the leaders in their industry and give you a chance to build your authority within the community over the period of time.
Option 1:
I think this is something here many SEO firms and freelancers are focusing already but i still think it needs more focus and concentration. If a business plays a vital role on 3<sup>rd</sup> part websites like stay action, reply to questions and reviews and communicate with the clients on regular basis i believe this can seriously help businesses get some serious leads.
This will be a great option for local business who offers services within a limited area. Websites like Google Maps, Yelp and other yellow pages websites are great in that case...
Option 2:
Portals or websites like Trip Adviser or more are helpful but one need to spend some major time there... I personally don’t think that many people are investing their time on building strong presence on these websites, although business with limited online marketing budget should focus here specially websites from travel, Real Estate and hotel niches.
I think service providers (this goes to me too) should invest more time building strong presence there because i think many people use these kind of portals before making any decision so I think building strong presence will make a difference.
Option 3:
This is the most interesting and time taking at the same time. Websites like SEOmoz who are the industry leaders in their particular niche but does not offer SEO services are great place where you can build your brand. This can be possible by being active in the community, commenting to daily blog posts, writing guest posts on the blog and building strong and communication with the community not only on the platform but on other channels like twitter facebook and emails.
This will help you build yourself as an expert within the community and you can get a chance to get more leads for your business.
Hope this helps, love to listen your point of view on this...