As we can see, a good sign up form is a tricky thing, it isn’t just a nice UI design. To improve users experience, a designer needs to think about all the details of the process. A properly made form can increase conversion and decrease clients abandonment.
Filling a form is also about momentum. In many cases, I take a print out of my forms and ask a few personas in my team to fill the form. If they are struggling to fill it on paper (for clarity, space, momentum), I need to see the form design again.