Advertising on blogs can be focused on the blog itself, the feed, or on the post.
Blog-centric advertising treats the blog as the main element for revenue. The concept behind this is to capture people who physically go to the website to see the ads. This usually requires placing the ad code into the blog template, and depending on your blogging platform- knowledge of HTML. Google AdSense ads that you see along the top or sides of blog would be an example of blog-centric advertising which is also content driven.
Blog-centric, content driven advertising looks at the overall content of the blog and tries to identify advertisements that would be appropriate for readers based on keywords found throughout each page. This type of advertising can be very successful if you blog has a focused topic such as blogging, or computers, or recipies. This type of advertising can fail miserably on sites or even pages in sites where the content is highly varied, not keyword rich, or misleading. For example, I have a website www.wildrosesgarden.com. This is my 'pet' site where I share my passion for spirituality and holistic health and wellness. While the adsense ads for most of the site are appropriate, they fail miserable on some pages that are designed for navigation or organization purposes and have little content other then a couple of links to other pages on the site. Generally those pages get ads about roses and gardening which is completely unrelated to my site content and only related to the domain name.
Feed-centric advertising is designed to attract people to ads in RSS feeds. These ads are not visible on the blog/website, and are only visible through RSS readers to the blog subscribers.
Post-centric advertising is focused on a combination approach that will captivate attention from people at the site, as well as subscribers to the RSS feed. Ads are placed within the blog posts individually, and these ads will flow through to the RSS feed where they can also be seen. An additional benefit to post centric advertising is that it can be tailored to the specific post topic rather than the page as whole. This type of advertising will be much more effective then blog-centric advertising on sites where the content is very diverse such as a personal experience site. I have another blog about Work at Home opportunities, businesses and telecommuting jobs called the Work at Home Center. While the site has an overall cohesive theme, individual post topics vary greatly from advertising small businesses to medical transcription to telecommuting, etc. This can also make blog-centric advertising in-effective because each post has a very different topic and keyword density. This is another example of when post-centric advertising can be more effective. Finally, post-centric advertising is highly embeded advertising that blends well with the site which encourages clicking because it appears more like content than advertising.