The Form Is a Conversation, Not an Interrogation
Most forms are designed from the database's perspective. They ask for everything the system needs, in the order the schema demands it. This is backwards.
A form is a moment of negotiation between a user's goal and a system's requirements. The user has something they want to accomplish. The system needs certain information to accomplish it. A well-designed form closes that gap gracefully. A poorly designed form makes closing it feel like bureaucratic punishment.
The most common mistake: designing the form from the system's perspective. The database has fields. The form gets fields. The user fills the fields, presumably understanding why each one is necessary. This is not a conversation. It's an interrogation conducted by someone who doesn't have to answer your questions about why they're asking.
Designing a form as a conversation means sequencing questions in the order a human would ask them, grouping related information naturally, and — critically — only asking for what is actually needed to deliver the value the user came for. Every field not strictly required is a friction point that reduces completion rates.
Progressive disclosure is the form equivalent of natural conversation. You don't ask every question at once. You ask the foundational questions first, then deepen based on the answers. Shipping address fields that only appear when the user selects 'ship to a different address' aren't just convenient — they communicate that the system is paying attention.
Inline validation, not end-of-form validation, is non-negotiable. Telling someone their email is invalid after they've filled out fifteen fields is a failure of basic conversational courtesy. You wouldn't let someone talk for five minutes before informing them they're in the wrong meeting.
The form is often the highest-stakes moment in a user's interaction with a product. It's where they commit. Design it like you understand what that commitment costs them.