Remember, data collection is a two-way street. People won't give you their data for anything. So, think about how you are managing your subscribers' expectations. How clear is it to new recipient what they are going to be receiving from you? Try and get a good a feel for the experience of the person receiving your data collection methods as you can at this point.
When it comes to deciding how to craft that perfect subject line, there appears to be really only one area to avoid: the subject line of 60 to 70 characters. Marketers refer to this as the “dead zone” of subject length. According to research by Adestra, which tracked over 900 million emails for its report, there is no increase in either open rate or clickthroughs at this 60-to-70 character length of subject line.