According to Wiki "Keyword density is the percentage of words on a web page that match a specified set of keywords" So Create keyword specific content, thats the only ethical way to increase the density of keywords. Definitely title tag is an important consideration for search engines. You have a great possibility for listing in a short span of time in all major search engines for low competition keywords, if your keyword is included in the Title + Domain Name + METAs + content. Another tip is give Keyword based ALT tags for images. Try to build links to the site with Keyword based Anchor texts.
Don't overdo it though. Don't have keywords in there more than twice (and I'd also not do more than one twice -I usually go with each keyword once, twice being an exception).
you can use your keywords in your * meta tags (keyword and desc.) * if you have related pictures , using in alt tags can be an alternative