To get back to the main Topic , here's another great article about call to actions on your landers.
--------------------
Use an alternative colour
Colour is an effective way of drawing attention to elements, especially if the rest of the site has a fairly limited palette.
Things (the GTD application for the mac) does this expertly on their website. While the rest of their site is predominately muted blues and grey, their calls to action are highlighted orange. This extreme contrast leaves you in no doubt as to the next thing you should do.
http://boagworld.com/design/10-techn...all-to-action/