Here what I use.
Options +FollowSymlinks
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)?domain.com(/)?.*$ [NC]
RewriteRule .*\.(mpeg)$
http://www.domaintoforward.com/ [R,NC]
the domain.com is the domain that you allow video viewing. The Rewriterule is where you want to forward traffic from the website that is hotlinking you, like a paysite. You can also add hotlink.jpeg that the end with a message.
the mpeg is the ext of the files you want to protect.
Work very fine for me, but I'm using it on my httpd.conf with directory condition
<Directory /.../.../.../>
</Directory>