Use color orange as color for your call to action and form buttons (belcher button). It is highly proven that most users often click orange buttons according to Digital Marketer’s 43 split test.
Use blue backgrounds. Blue and brown colors give a trusting feeling towards user.
Put your Opt-in form above the fold.
Also put a Call to action below the fold.
Use clear images to indicate what you are trying to sell.
Use san serif fonts because of it’s readability compare to serif fonts.
Use subtle arrows to draw the user’s attention to the opt-in forms.
Don’t use tiled backgrounds. It’s a NO-NO.
Contrasting button colors. The color of your button should be contrasting to the color of it’s background to grab the users attention that will increase rate of users to click the button.
Put horizontal opt-in bar across the page.