From what you guys are saying, it is clearly best to optimize a post for one(and only one) keyword at a time. That of course includes its long tails. Otherwise it the post would look like crap. Lets say you wanted to optimize for 3 different keywords. That would mean that 15 % of the text was keywords, which leaves a limited amount of space to get the flow in your text.. Am I right?
Formula as below keyword density = number of keyword / total words Let's say your keyword is "forum", your article length is 1000 words, "forum" appear 50 times. Then your keyword density = 50/1000 = 5%