1st choose a domain and find a host, a probider you choose will depend on the content you plan to promote.
Once that has been taken care;
You will then need to choose a suitable cms, such as wordpress (wordpress is recommended)
Once that is installed you should take care of SEO on it before anything else.
You can find everything plus more for seo'ing your blog here
http://www.mytypes.com/seoblogtempla...ess-seo-guide/
There are also several SEO plugins that i suggest you install for best results.
http://www.mytypes.com/seoblogtempla...s-seo-plugins/
Once you have done that, its all down to looks.
100's of themes are available on the main wordpress site or you can just google "free wordpress themes" (unless ofcourse you want to pay for a custom one)
Now that you blog is installed, seo'd and looks good its time to find a suitable sponsor for your content.
There are hell of alot of sponsors around If you plan to promote teen i can ohnestly recommend
http://www.teenrevenue.com/
Or for other sites, i can suggest
http://www.cecash.com/
Both of which seem great!
If you want/need more of a different niche, let me know!
Or you can just search the gfy forums for suitable sponsors.
Hope that helps, my icq is in my sig if you require any additional help mate.