Sorry Guys couldn't resist the headline... but it is relevant to the post here, as I came across these videos as I'm on the mailing list of wordtracker (I'm sure some of you may be also).
They are promoting a book about headline writing to get click through, they interview the author in the videos below.
Whilst they discuss headlines in an SEO context, I think its equally relevant here...
Whether you want to spend $24 on the book is up to you, but there are a good few tips in the videos, worth taking 15min break with a coffee, and watching them
I hope you find them useful 
http://www.youtube.com/watch?v=u9QMiHSYglI
http://www.youtube.com/watch?v=_QJC467tI5A