Start with Intent!
Sean Fiene, Nintex Tech Evangelist has put together a set of forms design videos that discuss how to plan your Nintex Forms so people can easily use them.
You can see the first of the videos here:
For the rest of Sean's Nintex Forms Design videos, please go to the Nintex Learning Center and open the course How to Design a Form.
For detailed guidance on creating Nintex Forms see our Help Files and SDKs.