Randomized controlled trials (RCTs) are considered the most methodologically sound methods of conducting empirical research, but a successful RCT is contingent on the recruitment of subjects into the intervention and study. Few research articles and evaluations in education discuss recruitment, and even fewer discuss challenges in recruitment. This is worrisome, given that recruitment can jeopardize internal and external validity -- the most valuable aspects of RCTs. This paper initiates a conversation about planning and carrying out a successful recruitment campaign, specifically in postsecondary settings where students are more autonomous, programmes are likely to be voluntary, the flow of information is disparate, and incentives are often misaligned for external evaluation. We also share our challenges and lessons learned in recruiting students for a student support programme and its evaluation. We also advocate that more researchers devote attention to, and sufficiently plan for the recruitment of subjects into RCTs.