One thing I always recommend to clients is that they make sure their websites have a “call to action.” What does that mean?
A call to action is defined by what you want your site visitor to do. Do you want him to buy a product? register for an event? contact you? etc. You offer your website for a reason. Make sure that reason “calls out” to the user to increase the likelihood that you get the action you want.
You can have more than one call to action at your website, but no page should have more than one. Competing calls can lead to decreased action on all of your calls. Keep your pages focused on one call to action, and make it easy for the user to act.
Here is a great post about how to design good call to action elements: http://www.leemunroe.com/call-to-action-buttons/ It offers terrific real life examples of sites that have call to action elements to model.
Of course, as communicators we often have more power over the words than the design elements. A good call to action uses an action verb and is very clear. The text should stand out from the rest of the text on the page.