Preserving form field values between pages/tags

Hi, I'm building a form page that has 3 tags for different types of fields (i.e. Personal details, location details, other). I want to preserve the values of the filled in fields as the user moves from section/tag to section/tag. I've tried making each tag a separate page and use the URL to pass values, as well as put it all on one page and hide fields (which became more trouble than it was worth!). Does anyone have a more practical/useful way of preserving field values from page-to-page... or hiding fields as a user clicks on each tag? Thanks, -Nelson