If you're referring to Ad copy, I'd recommend reading the book "Cashvertising". It's the most Ad Copy direct book I've read. Very helpful and worth reading more than once.
Other tips depend on your brand and message. For example, emojis test surprisingly well for getting attention and performance increases, but so do the colors in the ad. It just takes some A/B testing to find what works best for your market and industry.
Offering something in return for nothing also helps build trust and creates a connection. Running an Ad offering a free ebook on a popular interest in your niche followed by a retargeting article that is value packed will instantly give your audience a positive authoritative impression of you. At that point, even if they don't buy from you, they will relate your name/brand with that topic and in the future when they need that service they will think of you.