Great post about Fog Creek’s development process for Trello. One particular item that stood out is the foundation of their design process:

We use a product planning board that has a list of problem-oriented cards. Cards are titled in the vein of “I can‘t find this feature” or “I want to do this thing but can’t”.

This is a fantastic way to understand how people truly use your product and the pains they are experiencing. This is in contrast to “idea driven” design where people just come up with cool ideas.