As far as Google SEO goes, which keywords should be put on home page? secondary pages?

For search engines there are no "secondary pages". EVERY page can be a "home" page.

It's only the mistaken belief of "experts" who consider the "home" page to be different.

I agree with Chris answer. Google ranks pages and not sites. So to Google home page or blog article or any other page for that matter is considered the same and will rank individually for their own keyword.

Well said Chrishirst, for every search engine whether it is Google, Yahoo or Bing, each page is home page. So don't think of inner pages as different from home one. And as far as the keywords are concern then they are meant for giving a clue to search bot about the content of your page. So try to make a bridge between them as they are too interrelated. Keywords are basically those words that acts as a backbone of your content.

High search volume and high competitor keyword put in home page and in secondary page select a page related keyword.