I have several custom fields (pickers, textarea, text field) in a NP form I need to validate. I've done it (validation) with FormIt but I'm not sure if the NP form works in the same way as a FormIt form.
At present, NewsPublisher doesn't have any way to validate custom fields, though it may in the future. I usually write JavaScript validation myself and prevent the form from being submitted with invalid data in those cases.