I have three radio-buttons for "kind of project":
I also have text input "Organization name" below the radio buttons.
"Organization name" input should be disabled if the user chooses "personal" project.
I think I should initially leave all three radio-buttons unchecked and require the user to check one of them, when he submits the form.
Should "organization name" be disabled initially, when no radio-button are chosen?
Alternatively, you can use a select dropdown instead of the radio inputs. By default, select will display a placeholder "Select Project":
The input will be disabled by default.
When user selects anything other than the "personal", the input will be enabled:
I believe this will be more intuitive for the user.
Default the radio button to the most common option unless the risk of the user selecting the wrong one is disastrous.
As mentioned by @Andrew Martin, hide the field unless it's relevant, this helps to declutter and provide focus on the fields that are important to the user. This should also decrease the time taken to complete the form and likely to increase conversion rate.
Disabled fields cause confusion when user's don't know what to do to enable them.
