如何使用htaccess将wp-admin url重写到其他文件夹?

I tried to rewrite a simple RewriteRule but i guess it doesn't turn up good. I created a htaccess file in wordpress wp-admin folder and i tried to rename the wp-admin directory name in my localhost.Here is the code i tried

RewriteEngine On    # Turn on the rewriting engine
RewriteRule ^wp-admin$ hello

Just for testing i had done this in my localhost. I want to start from simple pattern not complex pattern so i tried other simple pattern wp-admin and replacement as hello

  RewriteEngine On    # Turn on the rewriting engine
  RewriteRule wp-admin hello

When i go to http://localhost/my_site/hello i can't able to direct to wp-admin for this am getting 404 error. When i try http://localhost/my_site/wp-admin am getting internal server error.

I think the rewrite rule is not good in my try. I have one more doubt should place the .htaccess file in the wp-admin directory or in the my site root directory in my_site or should i place in every directory which am trying to change the folder name on the fly.

What wrong am i doing here.Any help please?

RewriteRule ^hello(.*)$ wp-admin$1 [QSA]

Will change:

http://yourdomain.com/yourwp/hello
http://yourdomain.com/yourwp/hello/path/in/admin

to

http://yourdomain.com/yourwp/wp-admin
http://yourdomain.com/yourwp/wp-admin/path/in/admin

The QSA flag is useful for compatibility.

Here is my wordpress .htaccess with only one custom redirect, but you can understand the idea:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteRule ^login/?$ /wp-login.php [QSA,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress