As I said in our last email together, if your emails don't get through to your potential clients, they don't do you any good.

And it's the same story if they get through, but they don't get opened.

I've found over the years that the number one factor that determines whether people open your emails is your reputation.

If you regularly send useful and interesting emails, people will open them when they see your name.

And obviously, the reverse is true too. If you send nothing but sales pitches, or your emails just don't have enough value and interest in them, then people will stop reading them.

All that said, you can get a “bump” in open rates by using a good email subject line. And especially through the use of curiosity.

So here are 5 techniques for building curiosity into your subject lines that you might not have seen before:

1. Schadenfreude. It's human nature to be interested in someone else's misfortune. Some of my best open rates ever have come from subject lines like “My WORST sales meeting ever” or “My email disaster”.
2. Curiosity adjectives – e.g. “The surprising secret of great leaders”. Hint that what you're about to reveal is something they won't have seen before with words like surprising, unusual, weird or “off the beaten track” (ahem).
3. Use demonstratives – e.g. “Do you make these mistakes in English?”. Words like this, these and that immediately make you wonder what they're referring to. Which mistakes in English? What fatal flaw?
4. Surprising links – e.g. “Leadership secrets from Charlie Chaplin”. We've all read a million articles on leadership secrets from Winston Churchill so we don't expect to learn anything new from them. But Charlie Chaplin? Bring it on…
5. Hyper-casual language – e.g. “Oops” or “How you doin'?”. Using subject lines that are much more like emails you'd send to a friend sneaks in under the radar and makes people wonder what's inside them.

Any one of these techniques can give a little shot in the arm to your open rates and boost them above their normal level.

Don't overuse them: too many clickbaity “One weird trick” and “Hey” subject lines and people will begin to start ignoring them.

But used sparingly they can be very powerful.