Ranking for keyword constantly going down

It may due to the updated Ranking algorithm of Google. Build more quality links that helps you.

 

It is difficult to build links. Does anyone have any suggestions?

I'm not fond of the link building services sold here. Such as those 100+ link packages. Seems like spam to me.

 

Backlink to your site and build backlinks to your backlinks to improve them.

 

I already do that. Every article has at least 1 or 2 links to another article to my site.

 

I have the same case

 

Crazlunatic, it is good that you do not wish to pay for backlinks. Usually, you'll get links from unrelated sites, and while you may rank higher for a month, you will disappear out of Google soon.

Here's an article from Seo moz and backlinks - http://www.seomoz.org/blog/link-anatomy-understanding-the-value-of-a-link

And here's a long guide I wrote on my site (no advertising) - http://www.the-website-guide.com/the-ultimate-search-engine-optimization-guide.html

Forums, blogs, social directories & bookmarking sites are the best. Now to go even deeper, these sites I recommend:
Forums = Digital Point and related to you, Blogs = Strictly related to you, recommended to have a higher PR but it's not important, directories = Ezine and ArticleBase (no more) and Digg. Then either a Facebook and/or Twitter account.

I've seen people ranking MUCH higher only because of Twitter links. They do have 500+ follows or sometimes even more, but their twitter account/website sometimes gets in the top 5 for very competitive words.