I'm not sure if this is a copywriter question, but I'll answer it anyway,

I wouldn't worry about keyword density too much - it's been widely known that packing in keywords gets you flagged as spam fairly quickly. I mention my keyword a few times, and try to include at least one anchor if I can.

Which brings me to the inserting links - insert them as anchor text. Not too many. I prefer just doing one per article myself.

Length for a standard article is 400-700 words. Any smaller and its not an article, any bigger and it might not be fully read.

I focus on one keyword per article myself - try it out and see what gets you the best results.

let me know if this helped you
Danielle

In response to your questions:


what keyword density? - I would keep keyword density between 1% to 2%

how should I be inserting my links to my site? - Make sure to use proper anchor text when inserting your links. Some directories allow links in the body while others just allow them in the resource box.

recommended length? - This depends on you. In general, you can never go wrong with at least a 500 word article.

should each article only be focused on 1 keyword? - You can have 1 main keyword to focus on, yes. This should be as close to the start of the title as possible, for better SEO.


Hope this helps!