RewriteEngine On
# Redirect /index.php to / (optional, but recommended I guess)
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /.*index\.php
RewriteRule ^index.php/?(.*)$ $1 [R=301,L]

# Run everything else but real files through index.php
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ index.php/$1?%{QUERY_STRING} [L]