What are some ways that I can use A/B testing?

Testing is ongoing and endless. We test new features such as additional form fields in a lead form. We test multiple CTAs to decide which produces the best results. We test button color, test, size, and page placement to see where we maximize clicks. If you add functionality to a website, you may want to test if it positively or negatively impacts other KPIs. We test mobile first layouts. The possibilities are endless.