You better believe the advice I am talking about is from Rand of SeoMoz. Would you expect anyone else? You can read the full article about Keyword Usage and Targeting. He explains it really well and helps us to understand the basic fundamentals behind keyword usage and what is too much and too little. This is the process he recommends:

1. Use the keyword in the title tag at least once, and possibly twice (or as a variation) if it makes sense and sounds good (this is subjective, but necessary). Try to keep the keyword as close to the beginning of the title tag as possible. More detail on title tags follows later in this section.
2. Once in the H1 header tag of the page.
3. At least 3X in the body copy on the page (sometimes a few more times if
   there’s a lot of text content). You may find additional value in adding
   the keyword more than 3X, but in our experience, adding more instances
   of a term or phrase tends to have little to no impact on rankings.
4. At least once in bold. You can use either the <strong> or
   <b> tag, as search engines consider them equivalent (note: at
   this time we’ve only actually tested Google for the <b> vs.
   <strong> equivalency).
5. At least once in the alt attribute of an image on the page. This not
   only helps with web search, but also image search, which can sometimes
   bring valuable traffic.
6. Once in the URL. Additional rules for URLs and keywords are discussed later on in this section.
7. At least once (sometimes 2X when it makes sense) in the meta
   description tag. Note that the meta description tag does NOT get used
   by the engines for rankings, but rather helps to attract clicks by
   searchers from the results page (as it is the “snippet” of text used by
   the search engines).
8. Generally not in link anchor text on the page itself that points to other pages on your site or different domains

If you are looking for better advice and steps than that for Keyword Usage good luck. That is as basic and fundamental as it gets. And though it sounds simple, truly instituting this process can be difficult. But you want to spend the time and research necessary to do this. Don’t forget however that your content still needs to be engaging to the reader at the same time. It needs to interest people, not just the search engines!