The subject line is the first thing people see when your email hits their inbox. It’s all they have to go on when they decide whether to open your email, ignore it, or even mark it as spam. That makes coming up with a great subject line arguably just as important as the content of your email.

But creating an effective subject line can be tricky. You may worry about what secret “gotcha” words will send your emails straight to the junk folder, how long your subject line should be, and how to come up with ideas quickly.

This checklist provides quick tips for crafting subject lines that your prospects will want to click.