I recently received an email where a graduate student is trying to ask original authors for data. There is some evidence that authors withhold data due to time constraints (Tenopir et al. 2011), but they may also decline to share data because they fear a damaged reputation when a replication of their work fails (Lupia and Elman 2014). From my experience in the Cambridge Replication Workshop, authors are more willing to share their data when the replicator is perceived as trying to be helpful rather than cross-checking results. Here are my tips.