ajaykbansal on "Top Post, Subcategory on sidebar"

Dear friends,

Here is what I need help from this experience community :)

1. I am creating a knowledge portal using WP.
2. I have about 10 categories and 50 sub categories.
3. On the main page, sidebar will show only categories and top posts.

Now the question :
1. How do i select which posts will appear on front page?
2. When someone clicks a category, a new page opens. At that time, on one of the sidebars I would like to show all of subcategories for that category.

How do i achieve these?

Thanks
Ajay