webfeatseo is correct, don't try to stuff the keyword as that used to work a long time ago however things have changed a ton in the last few months. Jump out to Google Keyword Suggestion tool and pull a search up for that exact keyword you are wanting to try and rank for and then build a list of other related keywords that you can pull from to build with that you can build a theme based article that readers are going to understand and want to read.
Don't worry to much about how many times you use a word focus on the content you are writing. another good tool I found when writing articles is inboundwriter also SEOMOZ has a great tool that can help you analyze the page for accuracy called **On-Page Report Card **found on the http://www.seomoz.org/tools page.
I hope this helps.