Test. Different email clients and mobile devices display emails differently. Send test emails to colleagues, or use a testing program to make sure your emails are going to look good on screens big and small. Testing reveals design mistakes before it's too late, and testing programs can predict whether or not a campaign will get caught in a spam filter. You could even set up accounts with a few different email services for easy testing. Avoid sending one big image as a campaign, and cover your bases with a plain-text option for every email.
For example, you may analyse the journeys on your website and identify that people who visit a page is more likely to purchase than those who do not visit that page. With behavioural data pointing towards the potential for this page, it would be worth testing whether offering a bespoke content message or discount offer to users when they arrive at that page drives conversions. It could be that your customers have left items in their baskets and not completed their purchase, like this example here from Nordstrom:
Edit. Even editors need editors. When you're working on your publishing calendar, leave plenty of time for the editing and revision process. Once you send a campaign, it goes straight to the inbox, and you can't go back and update it. Newsletters contain meaningful content, and sloppy ones reflect poorly on the companies who send them. Grammar and style are just as important for email as they are for websites and blogs.
The downside of just making offers is that they’re not useful on their own. People on your list won’t receive any value from you unless they buy what you’re promoting, so they have little reason to stay subscribed. That’s why this email marketing strategy doesn’t work alone. And it’s why many e-commerce sites struggle to keep people interested. There are a few exceptions (e.g., Groupon) that rely entirely on making offers—but then the reason people joined the list was specifically to receive those offers.
For example, I can safely share that I listen to a lot of music, and I’m almost fanatic about sound quality. I might listen to an album with poor sound quality once, but I probably won’t go back to it. And to be clear, 95%+ of new recorded music has what I consider poor sound quality (due to an absurd standard of perceived loudness, which takes away natural dynamic range from the sound). That said, I’m not a hi-fidelity sound geek. I’m perfectly happy with my high-end studio monitors—I don’t buy $1,000 power cables, $5,000 CD-players, or $20,000 loudspeakers capable of playing back sounds too high for dogs to hear.
At worst, you might think I’m a bit weird for caring so much about sound quality. Or you might think I’m really weird if you knew that my loudspeakers are computer calibrated to my room. Or you might question my priorities if you knew I set up my office, so that my desk is nearly in the middle of it… mainly to be able to enjoy music better. But we’re all weird in some ways (and I’ll let you think this is the weirdest thing about me).