Summary: Meghan Ede has an interesting perspective on focus groups: as a way to get users to talk about long-term issues that would take too long to study directly. Here is a short note she wrote about her approach (reproduced with permission):

I find focus groups a good way to learn how people approach tasks and to get an overview of work that spans hours or days or longer periods. Focus groups can be a great way to learn about the work that occurs "between" or "around" the tools we build.
I usually start a focus group by asking people to tell me about their day. I encourage the other members of the group to record the speaker's activities on note cards so that I can concentrate on asking good questions. Then I help the group sort and discuss the note cards. The methods for sorting the cards vary with what I'm looking for.

I once ran a series of several focus groups with System Administrators. When I first asked them what they did, they said things like: install, upgrade, oversee, and troubleshoot XX Operating System. Their work sounded very technical, as if they spent most of the day in front of a computer.

When I next asked them to tell me about their last full day at work, starting with whether they had a cup of coffee in the morning, their answers were very different. They all launched into stories about how they couldn't drink coffee because they would be accosted on the way to the coffee machine with requests for help. Most of them carried notebooks to record end-user problems. They talked about telling users over and over again how to do the same simple tasks, like change passwords, or screen backgrounds. They talked about training courses and surfing the web, being paged at home and reading technical books in bed. They read incessantly; newsgroups, bulletin boards, whatever they could find, in the hope of finding answers to problems not yet encountered.

When we had the note cards sorted and discussed, the System Administration job was revealed as a job dealing largely with people, education, research and somewhat with supporting a computing environment. Almost a completely opposite picture from what they first told me.

I could never have learned this in a usability study (which asks if a specific tool does its job well) or in a survey (few System Administrator realize how much time is "lost" to answering unofficial questions). A customer visit would have taken days or weeks, not hours, and wouldn't have covered such a broad range of companies and positions.

Meghan Ede, meghan.ede@acm.org