One organisation moved from a two line form to asking for first name, last name, address 1, address 2, address 3, city, county, postcode, country, email address  (only first name, last name and email mandatory), with only a 10% drop in participation, and 60% of people providing their details voluntarily.

Others had seen a much bigger drop in conversions with a longer form, but had more success by placing the extra form fields (address etc) on a second page. That way the action itself had already been carried out with a minimum of data from the user, regardless of whether they carried on. Users were encouraged to see providing the extra information as part of the action.

And a single word can make a difference – this blogpost (from a company that sells software to help you optimise your forms...) shows how making it clearer that a field is optional doubled completion rates.

This article summarises a discussion on the eCampaigning Forum email list. Thanks to everyone who contributed.