In design research the people you talk to can be called participants, users, or informants. Regardless of the term you use, the idea is that you're learning from people other than yourself.
So, you know what you want to research and what needs to be done. Now, how are you going to go about finding people from your target audience to interview? The reality is, some projects are going to be more straightforward than others. Things you may need to define are:
Quality you're searching for (such as "regularly listens to audio books" or "uses a flip phone")
Depending on your research plan, you may need to define your desired informants in a statement such as:
Dog owners between the age of 32-42 who live in San Diego and visit a dog park at least twice a week.
Dog walkers with a minimum of 3 years professional experience.
You may end up defining your target interviewees with a few different statements to cover various applicable profiles.
There are a handful of ways you can go about finding people to interview, related to your study interest. Here are some possibilities to consider:
People you already know (although sometimes this can be awkward and hard to take seriously)
Friends of friends (this is ideal because they're "trusted" but you don't already know them)
Public postings (post a sign in a local library or shop; you can't always control who will respond, but if it's something related to a specialty, make sure you're explicit)
Hire a recruitment service (this is for companies with a budget)
Use an online recruitment service (this is for companies with a budget)
The most common way to find informants is to ask your network. This could be as simple as posting something on Facebook that says, "Any coffee lovers in Denver out there? I'd love to talk to you about a research project I'm working on!" .
As much as possible, you do want to reach beyond your immediate network, so asking your friends if they know "anyone who...." is even better! Sometimes the subject you're researching isn't particularly glamorous, so don't be afraid to let your personality shine through in your outreach:
Gearing up for my next user research study! Any Los Angeles-area friends work for companies that use t-shirt printers?? Sweet gift certificate involved for participants.
Last call for participants for a research study in the London area about t-shirt printing! Gift card to talk to me about labels for 1 hour! (What a great deal!!) Maybe your office manager has a contact? Let me know if you have any friends, family, or coworkers who might qualify!
It's the worst when you get to an interview and find out the person you're scheduled to talk to is not at all the right fit. Or maybe they only signed up because they heard about the incentive. You've driven an hour out of town, so already you've wasted A LOT of time. Now that you've learned your lesson the hard way, you'll plan better for the next time.
One way to do this is to make sure you clearly define your criteria for who you need to interview.
As you get more into professional projects a "screener" is a good way to help ensure your time is well spent because in asking a few simple questions up front it helps filter out people who are not part of your target research audience, while also helping to manage expectations. Steve Portigal, author of Interviewing Users, shares his version of the screener he uses. This document could also be shared with recruiting agencies when working on larger scale projects or when you're researching a set of users who are not easy to find.
Let's face it. People lead busy lives. Sometimes people want to help, but they just don't have time. Hence, a little bonus, or incentive, can make it more worthwhile.
This is something you don't have to worry about as a student (unless you want to treat someone to a coffee for helping you out), but in the real world you may encounter it depending on who you work for.
The other reality is no one ever has an endless budget to work from. A few different kinds of incentives you may find given in exchange for time/interviews once the session is complete:
Cash (although the finance department tends to hate this because there is no receipt to trace it)
Swag: t-shirt, keychains, USB sticks
Free pizza or coffee
This topic wouldn't be complete without addressing the legal side of things. This note is not meant to freak you out, but more to help you cover your bases and be aware should you ever find yourself working on a design team for a company.
Often; research teams have a waiver or a form that interviewees need to sign. In essence it's a "permission slip" so they're aware they're participating in a "test" or interview and that it may be recorded. It's not something that is often shared online because you need a lawyer to review it. Again, not all teams use one, because these research topics aren't classified information, but it is something you may encounter at certain companies.
Also, depending on your client, they may require you (or your informants) to sign an NDA, or Non Disclosure Agreement. This means you're not allowed to speak about any aspect of what was discussed outside of the interview. This is something that primarily happens with multinational or global corporations. Often the design team may know who the client is, but they'll frame the research carefully so that the informant doesn't need or doesn't guess the name of the client.