Why do many SERP hits lead to my main page, where there is no content?is a normal question. Many blog owners think that the search engines, as they index a blog, are executing one big magic trick.
Many bloggers think that their blogs will be indexed, and will appear in Search Engine Results Pages (aka "SERPs"), automatically. They are wrong, though - there is no magic here.
- Main page indexing, from "Index my blog!" requests. The more often you request re indexing, the more often your blog will be re indexed.
- Random indexing, from inlinks from other websites. The more inlinks you have, the more often your blog will be re indexed.
- Scheduled indexing, using a sitemap. The more often you publish, the more often your sitemap gets updated, and the more likely that the search engines will see a need to re index in the future.
You start out by submitting indexing requests to the search engines - either directly, or through one or more search engines submission services. Your blog is placed into a queue, and the main page is indexed. Until your blog has a reputation, the main page gets indexed, and that's it.
There are many search engines on the Internet. Each search engine indexes the websites on the Internet, so it can serve its customers - the people who want to read the websites. Each search engine wants to improve its own reputation for providing good results, so it's serving its own interests to provide results from websites with higher reputation, to people who search for websites.
Your blog gets a reputation as other blogs and websites link to it. A link from a low reputation website - to your blog - gives your blog some reputation. A link from a high reputation website - to your blog - gives your blog more reputation. When that website is being indexed, and the search engine finds a link to your blog, your blog is indexed. This may be a main page link, or an individual post link.
As your blog gains reputation, it gets indexed regularly, by a search engine, on its own. This is where providing a sitemap may be a key ingredient to getting your blog indexed - and this is where your individual posts are indexed, possibly based on a sitemap.
Until your individual posts are indexed, and they get reputation, most SERPs that lead to your blog will probably lead to the main page. You'll see similar latency issues when you rename your blog without properly planning for the change - you'll have search hit entries referencing the old blog name (URL) long after the blog is renamed.
Neither issue is magic, it's all logic. None of this is magic, in reality.