MarketPress - Certain products require custom data from shoppers

I've got a few MP users who have asked me about how to gather custom info for a particular product...

One client is selling an autographed book, and they need a custom field for people to input the name of the person the autograph should go to.

Another client is selling a product where they need custom fields for "organization name" and "organization address" to accompany the product. (Like for engraving or licensing reasons.)

How can this be done with MarketPress?