In this article, Chad White provide some tips for testing your subject lines. He also posted some great tips if you're looking for inspiration for your next subject lines:
- Repeat or tweak successful subject lines from your past campaigns.
- Pay attention to the searches run on your Web site and the organic searches that bring you traffic from major search engines. Consider using words from the most popular searches in your subject lines.
- Mine the subject lines of your closest competitors for ideas for words and phrasings.
- Take note of headline constructions used by newspapers and magazines, especially in their online editions, which some are now optimizing for search.
Tamara Gielen is an independent email and digital direct marketing
consultant with over 10 years of experience in online, email and direct marketing. 
It is also important to warn about just flat-out bad subject lines. The fact is, that even your best subscribers only have time to read the headlines (your subject line) and, even if they do not unsubscribe, they still should have some exposure to what you are about.
For example, saying "November Newsletter" is sort of worthless as it says nothing to anyone except those who open and read the email which, unfortunately, is still usually a minority of email recipients of any given email.
Posted by: Neil Anuskiewicz | Oct 20, 2008 at 07:29 AM
Thanks Tamara. I should get into the habit of tweaking subject lines more regularly. I sometimes notice subject lines that make you want to open marketing mails that you may have received yourself and try and frame new ones based on those.
Posted by: Neil Sequeira | Oct 17, 2008 at 05:27 PM