The search engines do not have an aspect of their formula that says 3% density = first search positions, or anything of the type. Rather than concentrating on precise percentages, you should worry about organic, regular inclusion of your targeted keywords and terms. This implies that as you organize your material you should keep aim on your keyword terms that they appear sensible to be implemented. You might have a common guide for yourself, such as trying to include the keywords every 100 words, or once per passage or so, but you should not fear about striking a targeted percentage.
Here are a list of keyword tools that will be of help to viewers more such tools can be had for free at www.webtoolson.com there are a lot more tools on offer covering all aspects of SEO:
GoogleDuel Original by GoogleDuel
Keyword Density by SEO Chat
Keyword Density Analyzer by Stargeek
Keyword Density Analyzer by Internet Marketing
Keyword Density Analyzer by seobench.com
Keyword Grouper by wordstream.com
Keywrd Density Analyzer by Jim Tools