Pages http://en.support.wordpress.com/pages/ are static and are for content that rarely changes. They sit outside of the blog structure and you cannot post to multiple pages in any blog. There is only one main page for posts http://en.support.wordpress.com/posts/ in a blog and all posts will display on the main blog page. There is no way to exclude posts from the main posts (blog) page. The front page of the blog by default will display your posts (not pages) http://en.support.wordpress.com/post-vs-page/ in reverse chronological order, with the most recently published post on top. We organize our blogs by assigning Categories and/or Tags to Posts (not pages).
The most common misunderstanding is bloggers creating static Pages that do not automatically update and thinking that they will when they cannot and will not. Only dynamic pages (Archives, Categories, Tags) created by the software will automatically update.
1. Delete any static pages you created to function as "subjects" or "topics" pages.
2. Assign Categories and/or Tags to your Posts (not pages).
3. Create a custom menu
4. Add the dynamic Categories and/or Tags pages into your custom menu as menu items.
Here’s a link to a custom menu walkthrough > http://onecoolsitebloggingtips.com/2011/08/11/wordpress-com-custom-menu-walk-through/
There are many common errors, misunderstanding and misconceptions when creating custom menus and you can read about them here > http://wpbtips.wordpress.com/2011/12/19/custom-menus/