there are so many ways in SEO to promote your site.. if you need more visitors and want to increase your PR then Update site regularly Blogs Articles Press Release Forums Social Bookmarking Classifieds Directory Submission Try to increase Back links for your site with Do follow and High PR sites..
It looks that you already did the on-page optimization. So try to focus on getting links and have some content on it in order to increase serp ranking.
If you have your own site then you can do SEO for better check and go through all SEO strategies. Firstly, your site has good on-page optimization i.e meta tags should be better stuffed with Title, description and keywords. Now you have asked about keywords, then you can finaliza your own keywords according to your site requirement. Make a list of those keywords and then check there search volume in keyword tool which are free available on the web. After selecting those keywords, you can do Search engine optimization of those keywords for your site. 1--- Daily update your site with new content and also make a blog of your site which should be also updated with unique content. 2--- Link exchange with the sites of same category having PR should be equal or more than your site. This will increase PR of your site. 3--- Do social bookmarking, Article submission, forum posting, Classified ad and press release of your site. Article submission will also help to increase PR of your site