1. Use catchy adjective words. Add some flavour colour to your subject line. The stronger and thought-provoking your adjectives are, the better you get people to take action.
2. Use numbers. Start off your subject line with numbers. It draws people's attention. It's a great way to tell your audience how much exactly they're going to get when they open your email. Studies show that digits work better than words (So instead of writing “five”, write “5”).
3. Use popular search queries such as how-to or what is. Generally speaking, people are looking for something useful and relevant or to solve a problem they have. So adding HOW-TO or WHAT-IS to your subject line can entice them to take action and open.
4. Keep it short and focused. An effective subject line is short enough to convey the best message possible. The subject line must be concise, but at the same time descriptive. Remember that you want to keep your subject line shorter than 30-35 characters or risk it being cut off and not make sense in the inbox.
5. Never mislead. If your subject line doesn’t match your message of your email, you’ll lose credibility and tarnish your reputation. While it might be tempting to manipulate your subject line just to get more emails opened, it will only hurt your open rates in the future. It is unlikely that people will be fooled twice.
6. Don’t limit yourself. Read and listen to other people, but you should never lose your uniqueness in the process. Be creative and have fun!