Profile pages are overrated. Too many communities drive newcomers to fill out detailed profile pages before participating.
This is a mistake.
The fundamental thing you need from a newcomer is participation. Once a user participates in a discussion he has a reason to return (several times) to see what others have said. He might reply to those responses. It gets exciting, the newcomer gets hooked.
Completing a profile page feels like work. We don't like doing it. We put it off. If your members feel they have to complete a profile before participating, you will lose many potential members.
If possible, let members enter a username, e-mail address and a security question – then begin participating. Once they participate, began to care about what others think of them, they will naturally update their profiles because they want to look good. You don't need to force this.