Keywords in Headings and webpage contents

Heading Tag<H1></H1>

All search engines give great importance for the heading tag. So, if you have your keywords in heading tags, you are likely to add importance to your pages. Try to optimize keywords in all heading tags h1, h2, h3 etc. Body Content
Content in your web pages are the primary communication means between you and your prospects. While tweaking the content for search engines, you should take care not to irritate the readers with unwarranted repetition of keywords.
Always keep in mind that you should write the content for the readers and not for the search engines. If the content is good/relevant and if you follow all the SEO best practices, the chances of attaining a good ranking are bright.
Analysts say that around 4 to 6 % keyword density per page is healthy. You can properly place and optimize the keywords within this prescribed density.
You should not attempt to have hidden keywords (that is, optimize keywords in white colour not visible to the reader, but available to the search engines) anywhere in the page. If search engines find out the trick, they impose stringent penalties and your web page would not be shown in the results at all.