Keep your CTA, form fields and benefits ‘above the fold’. In other words, make sure all your pertinent landing page information can be seen on screen, without having to scroll down. (People don’t generally scroll - unless they’re very motivated to do so.)
Complementary (and contrasting) colours - Colour design is extremely important in optimizing your landing page. Use complementary colour schemes to make your page appealing to the eye. Make your Call-to-Action in a contrasting colour to stand out.