I have read a few articles on designing advert banners and they all say similar things. And from the experiance I have gained from designing my banners and running advertising for my sites, they are generally right. There are certain things that seem to make banners more popular than others.

1) Keep it real simple
I've tried everything to get the Gurkin's stores out to people from putting story titles and descriptions flashing over banners, to putting entire stories over banners. The most effective campaign I have had so far had 4 words on the banner - "click here to laugh." Most of my banners were getting a click thru rate of less than 0.1%. The banner with 4 words on it scored a click thru rate of over 1.0%. I have had this experiance with other banners I have designed too.

2) Tell users to do something
Blasting "click here" over a banner may seem tacky and obvious but it does work. Visitors see a banner and tend to ignore it. Putting "click here!!!" accross the front is telling the user to do something - and they listen.

3) Face facts, sex sells
No matter what you try to do, you will vary rarely find a banner that can acheive a higher click thru rate than a banner selling sexy celeb pictures. You just can't beat them (well ok the Spider Man trailer may be able to). Always think about how you can hint at things like this while getting your message across. A good example of this is Paranormal Deathmatch which uses the line "better than a dream of Carol Smiley naked."

4) Windows style banners
Designing a banner in a message box style such as you get in browser alerts and any Windows dialog boxes seem to do well. This one I can't explain. Maybe visitors pay more notice to these, maybe its just luck, or maybe its because sites that would get a good click thru rate anyway think it is better to do this and so do it on the off chance it works. But the result is that these banners seem to get better click thru rates.