Need help with specific mod_rewrite SEO friendly URL

I'm newbie with mod rewrite and needing to have a SEO friendly URL but I haven't found how to make long dynamic URLs nicer.

so far tried these and none is working:

Options +FollowSymLinks 
RewriteEngine On
RewriteRule ^concepts  index.php?sitesig=PT&page=PT_003_Basic_Concepts

Code (markup):

Options +FollowSymLinks 
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?page=$1 [L]

Code (markup):

Options +FollowSymLinks
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} !^www\.[a-z-]+\.[a-z]{2,6} [NC]
RewriteCond %{HTTP_HOST} ([a-z-]+\.[a-z]{2,6})$     [NC]
RewriteRule ^/(.*)$ http://%1/$1 [R=301,L]

Code (markup):

Sometime adding -Multiviews this way
Options +FollowSymLinks -MultiViews

Some others this line belows RewriteEngine On:
RewriteBase /


could someone gimme the hint to make of the following a NICE url?


first level of my navigation menu is like this:

http://mysite/index.php?sitesig=DEFAULT&page=DEFAULT_003_Basic_Concepts


second level navigation adds this:

http://mysite/index.php?sitesig=DEFAULT&page=DEFAULT_003_Basic_Concepts&subpage=DEFAULT_010_Content_Snippets

script is already coded with that long structure so I need a way to rewrite those ugly urls.

thanks a tone for helping