Rafal Tomal has written an excellent article on how to create effection calls-to-action. (A "call-to-action" is a specific action you want your visitor to take, such as "sign up for the newsletter" or "buy the book" or "go to this next page".) Be sure to read the whole article, because it's full of gold nuggets. Here in an excerpt.
"Ok, before we dive into talking about the design of your website, let’s think about getting attention for a moment. Why do you even need to get someone’s attention and why is it so hard that you have to use some kinds of visual tricks?
The purpose of most websites is to attract the target audience and call them to action. The action can be an email sign up, social interaction or a product purchase.
Of course, the action you want people to take is usually not that attractive for first time visitors. You can’t just invite people to your website by saying“come and sign up for my email newsletter!” That wouldn’t convert well…
So, it is the content that attracts your target audience. It can be a good sales page copy, your blog posts, infographic, free ebook, you name it.
Once you have them in, that’s the time when you want to point them in a certain direction, the next level of your conversion funnel.
Now, getting someone’s attention and calling them to take the action is hard. The bigger the commitment to make, the harder to convert. Different types of actions may also require different approaches.
For example, asking people to sign up for your email newsletter in exchange for valuable free content is much easier than asking them to pay for something.
A call to action with a smaller commitment can be more direct. You can put it right in front of your visitors in the form of a popup or a big top banner.
However, the same approach wouldn’t work well if you used it for your buy button on a sales page. You want to prepare your visitors, educate them, resolve their concerns and build interest before asking them to purchase your product.
That’s why that call to action should be positioned more strategically. You need to be careful not to convert too early or your visitors may not be ready yet.