Let's take a quick look at a basic, but often-forgotten, element of email marketing: the landing page.
How many times have you clicked on a link in an email ad (or a banner ad or sponsored search listing, for that matter) only to find yourself on a page where you just don't know what to do next? What you're experiencing, of course, is an advertiser who thought about their ad copy, the design, the placement - everything they needed to in order to get you to click - but didn't follow through and make smart choices about what would happen next.
This article from ClickZ about landing pages is a great summary of the basics. Print it out and stick in on a wall in your work area. Even experienced marketers something forget about these things, as some clicking on ads will show you.
You're investing time and money in getting potential customers to click a link - don't lose them!