Besides your content there are other places you should put keywords. These include in your page headings, such as what you put between h tags. Search engines are trying more and more to read a site as a human would so that they can better rank pages. Many now treat text that is in h tags or otherwise emphasized with more importance than other text. So you should always put keywords in your headings. Additionally sometimes people like to dress up their headings with images instead of text. You should refrain from doing this. Replacing text with an image may make it look prettier but it will do nothing but hurt your search engine rankings since search engines cannot read text from an image.
Other places to include your keywords are in alt and title attributes for image and link tags. You should use these as shown below.
Your alt and title attributes shouldn't simply be a list of keywords, but rather a short description that uses keywords. Using these attributes will also make your website more accessible for people with disabilities, so put them everywhere.
You should also never link to a page in your site with text like "Next" or "Click Here." Like using images to replace text all that this does is rob you of a spot to put keywords. always use meaningful identifiers in your links and in everything else.
By now you are probably used to me talking about keywords. I've told you to put keywords in your title, in your domain, in your URLs, and now in your content. I cannot stress enough how important it is to do all of this. Keywords make up a large portion of search engine ranking formulas and almost 100% of directory ranking formulas, so the more you squeeze in the better off you'll be.