If you really want a PC to do something inadvisable (for the hilarity drama), the best thing is to advise them not to do it.

Transcript

Luke: I'll see you around, after I deal with Vader.
Yoda: Know where to find him, you do not.
Luke: I... use my psychic link to Vader to see if I can locate him. Can I do that?
Obi-Wan: It would be most unwise to open your mind to Vader.
Luke: Obi-Wan? Are you haunting me?
Obi-Wan: No, I already told you, I'm a cloud of midi-chlorians. I came with you in your X-wing.
Luke: So that weird smell...?
Obi-Wan: No. That was R2.