Once the best key phrases have been identified the next stage is to check how many other people are using these phrases, (even the best key phrase is of little value if your website is buried among thousands of other matching sites) - you can do this by trying out the searches yourself with yahoo or Google, or you can use a site called word tracker. (see number 4 above)
Of course unless your site is extremely focused you will find that it is almost impossible to list all of the best key phrases within the recommended 400 characters of your Meta tags. This difficulty can best be addressed by creating separate sets of key phrases, (separate title, Meta description and Meta tags), for different areas of your site that focus on different topics. By tailoring your key phrases to the specific content you will also, 'win points' for consistency and density of terms.
Issue number 5 is really an extension of this same exercise, for we find that the more content we have to offer, the more key phrases become appropriate, and the more search engine results we attract. This reality, has prompted people to publish huge amounts of random content on their sites, (called spider food) - some even do so in a manner that is visible only to the search engines, but not to the human viewer. This practice has some value although there are two risks:
1 - Content, however voluminous, must always be relevant, and interesting. Poorly written, irrelevant or excessively lengthy diatribes serve only to scare off the visitor.
2 - Search engines are getting smart to this practice, and are likely to mark a site as 'spam' if its content seems unduly broad, or if hidden spider food pages are found.
Number 6 has declined in importance in recent years, but is none the less significant. It was once said that the key to success with web marketing was to get your site listed in 500 places. That may be no more than an urban legend, but there is no doubt that being well listed and well ranked works to your advantage.