Relying on recruiting agencies to find people to interview in a research study could seem the easiest choice, but those samples of users aren't always the best people to deal with. Their engagement is purely based on the pay-back, and they consider participating to interviews and focus groups almost like a second job. Existing networks and digital media gives the opportunity to be more creative about the way in which we reach and engage research participants.
From sending a call for participation to lists of users already in contact with the client organization, to identify local hubs who could distribute the message through their networks, both ways allow to intercept people who already share specific traits, and are willing to respond to the call. Alternatively, posting an announcement that links to a recruiting screener on platforms such as Craigslist can also work well, especially if the aim is to find a sample with diverse backgrounds and social-economic conditions. Finally, social networks could be also a relevant channel: e.g. set up an Instagram page that explains the research scope and use a system of hashtags to find and interact with people who correspond to the target profile and are interested in that subject.
Using these alterantive strategies allow researchers to get in touch with people who are interested in participating to their missions, beyond the specific incentive. The research would benefit from the engagement of more motivated participants, who are able to provide honest insights.
Even if less expensive than recruiting agencies, all these alternative strategies are still quite time-consuming - they require to deal upfront with each participant one by one, build the dialogue, fix the appointments, etc. But it's worth!