These basic rules of thumb are the building blocks for a well structured article

Number of Words: At least 400 words. No more then 800.

Rumours are that Ezine privately prefer article >400 words

Title: Keyphrase at the start of the title - better for optimisation.

e.g. good - Dog Training - 5 Great Tips; not as good - 5 Great Tips for Dog Training

Lead paragraph: Very short, relevant and convincing - 160 characters.

The title gets them to visit the article. The lead paragraph convinces them to stay.

Paragraphs: Short and sweet - 50 -75 words max.

Keep sentences short too. Remember - they scan. Look no further than Travis for examples.

Subtitles: Google likes these, especially bold.

Make them relevant. Use a keyword in one.

Keyword: Density 1-3%. So for a 400 word article, that is 5 occurrences.

No harm in shuffling the words in the keyphrase around a bit to make it less like a sales pitch.

Concluding paragraph: Remember to offer a solution to the readers' problem, not hard sell.

Anchor the keyword within the call to action text.