Taking the time to interview your customers or potential users is a very useful method to truly understand their needs. It's not a complex thing but can be powerful for finding a truth about their behaviour that you otherwise may not consider, known as an 'insight'. An insight can be a powerful thing that shapes how you present your offering or service to users.
It's a chance to move away from your perception of the world and your company's internal views on how things are. This gives you the opportunity to see the reality of your customers' lives and thought processes. Good interviews usually take a bit of time to organise so it isn't something you'll be doing every week.
There are a few stages to organising successful interviews. It starts with deciding what you want to get out of the process as you can't cover every subject. Define what the focus will be and what areas of behaviour you're looking to understand. Is it a particular process or product you want to discuss?
Once the direction has been decided you should capture what you want to cover in a discussion guide. Essentially this is a list of questions you want to ask your interviewees and the topics you want them to talk about. Collaborate with others in your team to put this together and use it to get sign-off on the scope of the interviews. It will form the basis of your interviews but you don't have to follow it to the letter.
You'll also need to recruit your interviewees. You'll either want to find existing customers of your site or people you see as your target audience. For the former you should have some contact details of people who have purchased from you or who have enquired, whom you can reach out to. For the latter you might have to put out adverts to find them or get help from a user recruitment company. In both cases you'll probably contact more than you actually speak to, so expect to spend a bit of time on this. I'd aim for about 10 people in a set of interviews but if you've got the budget and time you can go for more.
When it comes to doing the interview, it can be done either in-person or over the phone/Skype. Start the chat off with some small talk and try to build a bit of rapport before launching into the questions. Then once you're in the conversation you should mostly stay quiet and encourage them to speak, as it's their experiences you're interested in. You should record the interview for playback later but it's also worth having two people do the interview. One can focus their attention on the interviewee and hold the conversation while the other can take notes of interesting points.
After the interview is done you should spend a bit of time reflecting on and analysing what was said. This can just take the form of the two interviewers chatting and comparing notes, before noting down key points of feedback. It's better to not wait too long to do this or things can be forgotten. If required these key findings can then be written up into a report for each interviewee.
Try and recruit a range of types of people that use your site, don't just settle for the easiest ones to find. Sometimes the best insights are to be found in the extremes and the users that do odd/unlikely things.
Be careful to avoid our old friend 'leading questions' (just like in Design Testing) and don't aim to use these interviews to confirm what you already think. This is a great opportunity to go in with an open mind and see what surprising ideas can come up (though don't worry, you don't have to use them all).
Some interviewees can dry up or give short answers. It's your job to encourage them out of their shell and make them feel comfortable to speak further. Try simple things like saying 'tell me more about that', 'what do you mean by...' and the classic 'why'. Often asking why several times gets you to the true reason behind a person's behaviour and that magical insight, so don't just settle for their first answer.
Be aware that people are bad at explaining what they would like and predicting the future. Don't get them to tell you what they want, instead get them to give you concrete examples of actual past behaviours. It's then your job to identify a solution that will help them.
Insights may not be all that revelatory when they appear so don't only be on the look out for something earth-shattering. They can be quite simple but they contain a kernel of truth about how users actually behave and think. Something as basic as 'customers will only buy if there's free shipping' can cause a huge shift in the way you sell.
Most of the tools here aren't going to be particularly fancy and are things you should feel comfortable using. You might want to write your discussion guide on a collaborative writing tool like Google Docs. Calendly is a very useful tool for allowing interviewees to book in times in your diary for the actual chat. The main tool for interviewing is just a way of recording it—probably on your phone—and notes can obviously be taken on paper and post-its.
Writing and setting up the interviews is the time-consuming bit and can take a few weeks. Each interview should be 30-60 minutes.
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Note: the examples in this guide are for website design, but most of the content is also applicable for native apps and software.