"Here is another study about effective subject lines - once again reinforcing the point that straight forward lines that indicate what's in the messages are the best."
This is consistent with the old public speaking saw that the first thing you tell an audience is what you're going to tell them. Some things never change. There are more factors mentioned, including the expectations you set with your audience, so check out the study.
While you're on MailChimp's site, you might take stroll to their free guide to e-mail marketing. Appears to be a fairly comprehensive beginners guide.