I am designing a registration form for a site with multiple sets of information required from the user. I have categorized the data fields into relevant groups. Now should I present the form sections in one go or follow a wizard-like approach? What things should I keep in mind while deciding on this?
I refer you to Luke Wroblewski's talk: - Sign up forms must die http://www.lukew.com/presos/preso.asp?25 where he describes some things to do and some really annoying things not to do.
If you need to do this, gradual engagement is key. Really consider whether you have to get all the information on the first sign up encounter, or can some of it wait.
The very fact that you are gathering enough info at sign up that you need to ask this question is an indicator that it's too much at once.
I visited a site recently, to sign up it asked me for an email address only. Nothing more. I got a nice welcome email thanking me, telling me more about what I could do, links to some pages of interest, telling me how I could get help, contact information, and a big get started button. If I wanted to make use of some more features I could add necessary info to my profile as required.
I think it can depend on form length but if all the questions are relevant and grouped logically the user will be likely to complete. Invaluable form best-practice research has been carried out by Luke Wroblewski and you can download a PDF here http://www.lukew.com/resources/articles/WebForms_LukeW.pdf or just google search for his work. I totally recommend it.