From Cynopsis Advantage:
An Information Interview is where a job seeker asks for career and industry advice from a known person within a particular field. The interview is used for several reasons: to learn about the industry, learn about a company, learn about a job, seek advice on how to better prepare yourself for the short and long term for the job and to network.
Informational interviews can be difficult to arrange because the job seeker is the one who asks for the interview. Some think that most executives have no interest in spending their time with someone they don't know, answering a slew of questions. But if asked with proper etiquette and respect, you'd be surprised at how many are actually willing to help, either by phone or by meeting for coffee or a drink.
Before contacting anyone about an informational interview, you have to do some homework. Research the individual, the company, and the industry.
Always remember the executive is doing you a favor so try to arrange a time and place that is convenient for them and set an amount of time such as 20-30 minutes.
Dress as if you were on an interview, prepare your questions but don't get anxious if you are running out of time.
If you are meeting for coffee or a drink, always pay the tab and offer to end the meeting at the agreed time, if they want to continue, great, but by you mentioning the time, you give the executive a graceful way to exit, something that everyone is always grateful for.
After the meeting is over, ask if you can keep in touch in case you need further advice and give them your business card with all contact info on it.
Make sure you write them a thank you note, and since speed is not a factor, a handwritten note might be more appreciated.
It's okay to take notes, but never, ever ask for a job or job leads. You will put the executive in an awkward position plus they will feel ambushed.
Start the interview with thanking them for their time.
Be a good listener and ask good questions.
If you ask someone for an informational interview and they say no, don't ask again.
The informational interview can be a tremendous tool in gained knowledge and networking, as long as you keep your personal need for a job out of the conversation. If you do ambush them, the executive will most likely shut it down and you will lose, what could have been, an exceptionally useful experience.