One of the most important tasks a PI faces is recruiting personnel for the lab. Which requires being able to interview applicants and the people they provide as references. Best advice I ever got on how to do this comes from a blog post on Forbes, which says (paraphrasing): The only important interview questions are: Can you do the job? Will you love the job? And will we love working with you? In other words: skills, motivation, and fit. All three have to be there, but fit and motivation are probably the most important. Skills can be learned, but motivation has to be there from the beginning. Also, when hiring programmers, look for people who write code for the fun of it. When hiring researchers, recruit people who know how to express an unpopular opinion without being offensive. You need employees who constantly challenge you and each other to do better but don't tear each other down when doing it. When hiring data analysts and scientists, be on the lookout for liars. Total honesty is absolutely essential in bioinformatics and data analysis, especially when results defy conventional wisdom or contradict previous results obtained in your lab. How can you tell if some-one is dishonest? It's easy. Just look for lies on their cv or resume regarding skills they claim to have. If they lie to you about something so personal and basic as who they are and what they know, they'll probably lie to you about other things, too, like their results. Lastly, don't reject an applicant because you don't like them on a personal level. Whether or not you like a new hire is irrelevant. You're not hiring to make friends. You're hiring to build a group that works well together and gets excited about coming to work every day. Your ultimate goal is to create a workplace that enables smart, talented people to do brilliant work...and keep doing brilliant work even when you're not around.