I have done this lots of time. But than also I am stuck here again (in a different server) and can not figure out what is the issue.
Completed htaccess editing
First check whether your apache is supporting mod_rewrite. If yes then add a .htaccess file. My codeigniter .htaccess file is:
DirectoryIndex index.php
RewriteEngine on
RewriteCond $1 !^(index\.php|images|css|js|robots\.txt|favicon\.ico)
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ ./index.php/$1 [L,QSA]
Finally in your config file, change your base_url, remove index.php from that if you have added.