To identify a lucrative app, assess user reviews, ratings, and download numbers on reputable platforms like the App Store or Google Play. Look for apps with transparent payment methods, positive testimonials, and a clear explanation of their earning model. Research online for user experiences and check for any red flags or scams associated with the app. Additionally, consider apps from established companies with a track record of reliable payouts. Always exercise caution and avoid apps that request sensitive information or seem too good to be true.