If I understand your question correctly, you are asking about information interviews. That is the term.
People are cooperative and like to show off what they know (I'm doing it right now!). So let them.
This isn't hard. Nearly everyone you call will be open to at least talking with you on the phone for a few minutes. You may have to schedule a time to call back or meet in person later, and that's fine.
So say there's a job you want to do, you think, and you'd like to find out more about it. The funny thing is, the same job done at different companies can be totally different experiences because of cultures. So it's best to talk to three or four people doing that job at separate firms to get perspective.
To find these people is not difficult. You can use LinkedIn. Or you can use a simple method called the Little Unsure technique, where you ask the receptionist, "Hi, I'm not sure who I should speak with...I'm looking for the person who does [whatever role it is]. But again, I'm not sure who that would be there..." and trail off.
This method is very effective.
You may get voicemail. 3/4 times the person you're calling won't be available to take your call. Don't take it personally. Leave a quick message or call back later now that you have the name.
For messages or live answers, say you are doing some research, are interested in the role they have and are wondering if it's right for you. If they could speak with you for about 15 minutes, it would be very helpful. If now's not a good time, when would work?
Have your questions ready. They may want to go ahead right now.
I have had employees get time for such interviews in person approved by their boss...again, people want to be cooperative. Once in awhile you may find someone who is "too busy". Simply move on. No big deal. That person is probably not a fit anyway.
The higher you go in larger organizations, the nicer the people you'll find. How did the leaders in most organizations get there? The Sales career path. They know all about cold calling. The appreciate it.
Nearly all of the success factors here are getting past your fears. These fears are simply not valid. They don't hold true in the real world. Nearly everyone is flattered someone would ask their opinion. Go find out whether this job is really something you want. And you'll also find out what kind of different corporate cultures exist...which will play a big part in your job selection, if you're smart.
Don't be in "I'll Take Anything" mode. Start sorting.
I've worked in sales and business development for more than a decade. In college I sold security alarm systems door-to-door, and worked as a telemarketer. Journalism is a lot like sales, you have to find answers, and there is more than one person who can give you the information you need--as long as you're willing to look. Fear of rejection is natural, but it's a matter of getting started, and being resilient enough to bounce back.
The best way to get in front of your prospects is to frame the discussion in ways that emphasize how they benefit from talking to you. Your goal is to help them solve a problem. A painful problem. When you demonstrate that you already understand some of the problems facing businesses in their industry, you enhance your credibility, and show that you've already done some homework.
Often industry associations or trade groups have a membership directory on the website. It's fairly easy to find websites and pertinent details even if the companies listed don't have have contact info. Some industries have major trade shows and conferences. The conference exhibitors are often listed in a program. This is a quick way to find out who is spending money to be featured in front of their fellow industry players, and who is already a leading voice. Finding exhibitor info is often as simple as a Google search.
I hope you've found this helpful. I'm happy to discuss some strategies with you on a call, if you have further questions.