Successful recording sessions require an understanding of psychology.
Specifically, singers in the studio, both new and experienced, can tend to freeze up in the booth. The idea that what they sing or play will be permanent can really get in their heads.
The most important reminder I try to give, especially for first-timers in the studio but really for anyone who isn’t a seasoned session singer, is that the recording is permanent, yes, but it’s also repeatable. You can make as many takes as you want to get the phrasing perfect, the tuning exactly right, the lyrics accurate.
To me, that repeatability takes off so much of the pressure of the studio. I can relax and get to work making a recording that expresses emotion.