You must have noticed while saving any of your WordPress blog post that it automatically selects default category and incase if your post is not appropriate for default category then what you do is unselect default category then select some other category. This tutorial explains you how you can reduce these unnecessary steps by making WordPress to automatically unselect default category when you first select any non-default category.
You simply need to install and activate the new WordPress plugin Categorized. After activation it instantly unselects the default category as soon you click a non default category for the first time.
There are no other settings and options, after activation you can check it working from your add new post page.