I have watched a few hundred people fill in forms, in usability sessions and in the field. They give up for the same six reasons, and none of them are about how the form looks.
1. It asks for things it does not need
Every field is a reason to leave. The Ledgerly filing step went from eleven questions to two by asking only for what the system did not already know. Completion went up accordingly.
2. It does not say why
"Phone number" loses people. "Phone number, so the courier can call if nobody answers the door" does not. One sentence under the label.
3. It punishes mistakes late
Validation that waits until you press submit, then paints the page red, makes people feel stupid. Validate each field when the person leaves it, in a sentence that says what to do.
4. It loses your place
A form that forgets everything when the phone's battery dies or the tab closes will not be started again. Fieldnote saves every answer as it is given; so should everything else.
5. It is one giant page
One question per screen on a phone, a few related questions per screen on a desktop, and a clear sense of how far there is to go. Progress bars are fine; "step 3 of 9" is better.
6. The button does not say what happens
"Submit" means nothing. "Send my application" or "Book the appointment" tells the person what they are about to do, and whether they are ready to do it.
Fix those six and the form will be finished. Then make it look nice.
