For me i go for Link Building, blog and forum posting!
i think forum posting & links building in relevant sites do a lot favor.
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If you could find a way to pursue each strategy, you would be on the right track. The key would be to prioritize which strategy suits your niche best and work from there. But, combining aspects of each is the way to go - in my opinion.
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Many good points have been given already but I go with blogs and social bookmarking. Try placing your feet on your targeted clients' shoes. Know what their exact need that you can to offer them. This way, you know where to advertise most.
Depends on what do you promote:
1. website where you get money from advertisement
depends on it, you should choose prioriry from seo, blog articles, links, direct marketing
"si-AdPlace Pro" - Text Ad Software
I guess, Forum Posting WINS because value is double
Forum Posting = Quality links building
Quality links building; is for Search Engine Ranking
Blog & Forum posting; is for Link Building and Promotion