Google Search Results

Can anyone advise, please?

When I add posts to my blog they are indexed very quickly by Google. However, I have noticed that sometimes the Google result links directly to the post, yet other times it links to the main blog and so the user does not find what they are after unless they search the blog (and many don’t).

I am not doing anything different that I am aware of when I add new posts.

Why does this happen, and is it possible to make sure that Google searches find the actual post and not just the main website?

Thanks