First Of All Learn what On Page Optimization is ?.what we have to do for that.It is Step by Step Approch.They Are

1. Find Keyword competitiveness research and competitor strategy analysis.
2.Optimize URL and Add keywords in URL.
3.ADD Meta tags To Our site.Which is very important factor.That is Title,Description,Keywords.
4.ADD  H1-h3 tags adjustment and implementation.
5. Bold texts which is keyword.
6.ADD Keywords in content And Give Hypherlink To It For Internal Pages.
7.Give Alt tagsFor Images.
8.Check Your Site With W3C validation.
9.Html and xml sitemap creation and submit to Google.
10.Keyword use and proper placement on home page.
11.Linking structure optimization.
12.Add robots.txt to your site.
13.Add Google Analysis,Google Webmaster Tools,And Google Places.
14.Add Google,Yahoo,bing,alexa Verifications.

learn more........http://www.webconfs.com/15-minute-seo.php