WordPress: Categories to Tags Conversion

I have to convert few categories to tags and put all those post which are holding the current categories, which are going to become tags, to new categories. We have facility in WordPress to convert categories to tags. You will find this link in Categories menu inside Post section. Please check at the bottom section.
By default, post with all categories converted to tags will be assigned to default categories, which is generally uncategorized. Now, I need to go to each post freed up in "Categories to Tags" conversion and assign them a new category. That was a difficult task. Post can be very new, or very new, I need to go to each other in order to assign them a category. So, I search a method to do this.

Page on WordPress Admin section to Convert Categories to Tags:
(See the link at bottom)

Category to Tag conversion

Category to tag conversion

What I did as follow for Categories to Tags conversion and assigning new categories to those post at the same time:

  1. Create a new category
  2. Assign this category to default category from setting->Writing
  3. Do category to tag conversion before deleting the category. Here only use those category or categories which has the post you want to assign to newly assigned default category. When category is deleted, the free post is assigned to that default category.
  4. Now, delete the category you want to transfer to new category.

So, your category is transferred to new category and old category is now part of tag. I need to do this when I want to reduce category list so that it can come easily on top menu. Currently I have removed it from the top. Assigning category and good tag is not always easy. I thought to concentrate on tags keywords. So, I have converted all Linux, Apache, MySQL, and PHP categories to LAMP category. and assigned those categories to tags. Otherwise, take for PHP, I need to use PHP word both for category and tag.

You need to repeat the above process for each separate categories. For new LAMP category, I need to do it once for all old category (Linux, Apache, MySQL, and PHP). and for new category "Web design", I followed the same process and assigned all HTML, JavaScript and CSS to "Web design" category.