When you are going to base important (and costly) strategic decisions on usability testing results you want to make sure you’re getting your feedback from people who match your target audience. You want it to be deep, unbiased, and accurate.

While enlisting family, friends, and employees as participants for your studies saves money and is better than doing no testing at all, there are disadvantages. People close to you may not be typical users, they may “know too much”, or feel uncomfortable telling you what they really think because they don’t want to hurt your feelings. When the stakes are high, it makes sense to invest money to recruit participants who are objective and who represent your target user.

Think of youself as a casting director

Usability studies involve fewer participants (10-12 are usually enough) so it is especially important to make sure you’re bringing in the right people. Focus on just one or two demographic profiles. Narrow down the user profiles to those target audiences that will be most critical to your product’s success in the marketplace.

Choose confident and articulate participants with passion and at least some expertise in your product category. Bring in people who are similar to your typical users. Try to recruit at least 2-3 “power users” who have deep experience with many similar products because they will provide robust feedback and perspective on the proposed design.

Does the participant have enough skill to complete the test?

Define the required foundation skills. For example, if you are testing an iPhone application make sure your participants are fluent at using an iPhone -- otherwise you may end up testing the iPhone platform rather than your application. Your criteria might include “participant owns an iPhone and uses it every day for at least six months.”

Finally, when accepting participants into the study, the recruiter needs to make sure that new participants understand what it means to take part in a usability study. Being in a usability study is very different from taking part in a focus group or interview. Full disclosure of procedures is an absolute necessity. Participants need to know that they will be asked to carry out typical tasks independently on a new product, and that the product team may observe the sessions. If eye tracking or other biometric data will be collected during the study, you need to mention this as well. The follow up e-mail to participants should repeat this information, so participants have an accurate picture of what to expect as they arrive at the session.