Give your customer something to be happy about

Design your projects iteratively. Small victories made up of useable features released to production can serve two purposes:

1. Give your user the chance to actually use the code and REALLY tell you the business requirements
2. Make the customer happy by delivering useable code earlier

I have found that it is difficult for users to tell you what they need from a blank canvas. But, it's much easier for them to tell you that they don't like something once you have filled it up.