Describe what you have to offer the customer. Why should they read? What did you promise them in the subject line? Tell them something cool. Make them laugh. Make them cry. Well, maybe don't do that...
Use a list to:
LINK TO A LANDING PAGE ON YOUR SITE (This is the really important part.)
Now wrap it all up with a pithy little reminder of how much you love them.
Aw. You silver-tongued devil, you.