Most effective method of asking questions to users signing up?

[Disaster Area]

I would like to be able to ask a couple of questions to users as they sign up on the forum I am deeply involved in running (such as "where did you hear about us"). I was wondering what would be the best way of doing this. Is there any way within the default xenforo options to do something like this? And if not, is there a plugin/add-on that could be used to do something like this?

 

[S Thomas]

You can create custom user fields and set them as mandatory. They will be asked during registration this way.

 

[Disaster Area]

You can create custom user fields and set them as mandatory. They will be asked during registration this way.

is there a way of making them not mandatory but still show during registration? The downside of making them mandatory would mean that users already signed up would have to then answer these questions.

Alternatively, is it possible to make it so that for accounts that are already registered, a default answer is filled in?

 

[S Thomas]

I don't think already registered users have to fill in custom fields which have been created afterwards (maybe if they change their profile settings). But yes, of course you can set it as optional, but still show during registration.
You might be able to set a default value for older users with a query, though.