It is not difficult to conduct an excellent informational interview with someone who has a job that is interesting to you. Here is how to go about it.
Assuming that the individual has agreed to meet with you for 20 minutes and has now either joined you for a coffee or is speaking with you over the phone - here is a script on how to make the most of the opportunity.
So you can see a few things about this line of questioning. It is personal because we want the individual's experience not just the general high level concept of the career. There are of course many other questions you may ask and I offer these just as a flavour of how you can conduct the interview.
A final question worth considering is also, "Is there someone else you know that you think would be worth me speaking with and if so, would you refer me?"
This is a great way to get good information on the nature of a career path or role. Don't expect the answers to be all happy or good. No role is perfect!