Some common mistakes when creating Facebook ads include targeting too broad of an audience, failing to use eye-catching visuals, writing unclear or irrelevant ad copy, neglecting to include a strong call-to-action, and not split testing different ad variations. Other pitfalls are overlooking the importance of mobile-friendly ads, directing users to a poorly designed landing page, and setting a budget that's too low to achieve the desired results. To create effective Facebook ads, it's crucial to define your target audience, craft compelling content, and continuously monitor and optimize your campaigns based on performance data.