A pure htaccess solution won't work against hotlinking (for the right-clicking). Actually, it would work (someone made me once one) but it will affect other things negatively as well.
There IS a solution with Javascript + htaccess like this one below :
This goes onto the pages you want to protect :
<SCRIPT LANGUAGE="javascript">
// Calculate the expiration date
var expires = new Date ();
expires.setTime(expires.getTime() + 1 * 60 * 60 * 1000);
document.cookie = "id=valid; path=/" + "; expires=" + expires.toGMTString();
</SCRIPT>
This goes into your htaccess :
RewriteEngine on
RewriteOptions inherit
RewriteCond %{HTTP_REFERER} !^
http://([a-z0-9-]+\.)*yourdomain.com/ [NC]
RewriteCond %{HTTP_COOKIE} !(^|(.+;)*)id=valid(;.*|$)
RewriteRule /*$
http://www.yourdomain.com/ [L,R]
But it's not 100% safe and even more important, most tgps & mgps ban javascript, so your galleries wouldn't even make it through the submission scripts.
There is another 100% effective solution, and you might want to contact me.
Michael