One way to get ideas for your subject lines is to view the archives of the lists. Anything that attracts Your attention is a good example. If it attracts you, it will attract others. Don't copy the subject lines out-right, simply use them as examples. Create the body of your message.
Some experts say long is better.
Some say short is better. I get results with both. You should have your URL link at the top of the message and repeat it throughout the message. Now, Don't Wait, etc. Many mail programs automatically make your URL address a hyperlink.