On Page SEO.

So I'm pretty new to the whole business game. I've been doing a lot of link building the proper way, and want to continue with On Page SEO. My main question is what is the best way to do this. Sorry if I've posted on the incorrect section, like I said I'm fairly new to this. Thank in advance.

The best way is to use a seo auditor on your website / pages with the main keyword you are targeting and adjust according to its recommendations.. they give a thorough seo 'relevancy analysis' from the address bar, to headings, keyword use/density, backlinks, and social popularity

Several popular ones exist if you search the forums such as SEO SpyGlass, Internet Business Promoter

Note: Spend some time on page seo but remember that the weight is only about 30% for search algorithms like googles.. quality content and relevant backlinking is much more important

First do On site SEO then go with backlinks, you don't have to much to do with On Site SEO, make good meta description, meta keywords its doesn't matter anymore, but you can put it also...
Watch does your site have 2 versions or more of index.html? watch does it work like www and without www...
Hmm get good content, don't care about keywords in your contet, don't write it for Robot, write it for Human Reader. ...

Instal plugins, optimize them and you are done.
You can also find very good plugin lists