Do properly structure your site:
Use all your H1, H2 tags.
Don't worry too much about keyword density
Create useful content
Use only royalty free images or ones you have paid for (unless you change the image in gimp/paint)
Do not make "thin" sites or MNS as google is cracking down on it. If you know what you are doing you can make those sites but you do not (at least not yet).
There are a hundred other things that come to mind and that is just onsite SEO. If you want real help then I would recommend using the search function to find SEO threads or show us an example of your site so we can figure out what the problem is.