Below are the four points to remember about keywords.

Prominence: Make sure that you place your keywords at the beginning of the content. They must always be in the first sentence.

Density: The keyword density must be at least 3% and not more than 5% of your total content. This is very essential as it affects page ranking in almost all search engines.

Frequency: The more frequently you place your keyword or key phrase in your content, the more relevance the search engines are probable to rank you higher on your keyword. But this doesn't mean you stuff the content with your keywords. Search engines will bar your site if you do this.

Proximity: Keyword proximity is as essential as all the above factors. Try to place your key phrases as closer as possible.

For instance, if your key phrase is "SEO tips", try to develop the content with "SEO tips" and not with other grouping of the words like "tips for SEO".

TIPS: Always use Google AdWord's Traffic estimator to find out how much a keyword is going to cost per click. Evaluate this number to the number of searches for your keyword. This will give you an idea of potential profitability of that keyword.