Avoid Asking What You Want To Hear

If you've got a pet feature, it's all too easy to drop it into a discussion of the proposed system when conducting interviews and focus groups with prospective users. The problem you then face is that it's easy for people to agree that said feature would be a good idea, even if it really wouldn't.

Firstly, you have to separate things that people think they would use from things that people do use. Consider whatever word processing software you use and think about all the features it has that you've never touched. When you bought the software, were you swayed by any of the discussions of those features in the marketing material? (The idea that word processors have more features than people use has been investigated by human-computer interaction researchers—https://www.cs.ubc.ca/~joanna/papers/GI2000_McGrenere_Bloat.pdf and while they found that some features go unused by some users, the users still know that those features...