I have an important interview this week and I happen to know my interviewer's information. I need some advice on whether I should add my interviewer on Linkedin before the interview. I am not intended to ask any question about my interview details. I am just not sure if it is a good idea to say Hi before the interview so that he may have more impression on me. Any suggestions would be appreciated.
View their profile, don't add them to your contacts list.
If you have your interviewer details, you have them for a reason - the company wants you to be prepared to the best of your abilities. For some people it means they also want you to see someone's face, or be able to know the name before the meeting, so you have one less reason to stress about during the actual interview.
View their profile, and also view a profile of other people who work for the company. Get familiar with the work they are doing, check people you might work with, check if they write a blog, or lead a podcast - if so, check it out too! You might use it to your advantage during the interview, you might learn a thing or two. Consider following the company you're going to interview to express your interests and proactive attitude.
Don't add them to your networking list on LinkedIn just yet. While it wouldn't necessarily hurt you (although you might be perceived as overeager!), it's better to wait for a connection request until you actually meet the person. Do that after the interview! Send the request with a post-interview thank you note. You might score some extra points, remind about yourself and get them a second chance to get familiar with the type of work you've been doing so far.
As an interviewing manager in tech, I have some candidates add me as a LinkedIn contact prior to interviewing. Well, or, I should say I have some candidates add me right before the interview; sometimes I'm interviewing people who have been connected to me for a long time (IMO the ideal case).
I don't mind it. My assumption is that they are trying to learn about the company and about me to determine their level of interest in the position and to prep for their interview.
If it turns out they're a grade-A psycho, which has only happened to me once in years of hiring, I can always drop 'em later.
So add them, but have a reason for adding them - if a candidate were to add me and then in the interview appear to not know anything about me or my company, I'd kinda wonder what their problem was and take it as a mild negative. Don't just add them to be "friendly" or something. Add a message about your intent, e.g. "Hi! I'm interviewing with your organization next week and I wanted to connect and learn more about you to prepare."
This might seem to be presumptive of you. On the other hand, it might be viewed as proactive.
I'd err toward being cautious and use what information that you can publically see - people who don't want to be stalked won't want to be stalked. People who accept all invitations probably won't bother looking at each invite to see who they are.
My manager refuses all LinkedIn connections simply because he gets so many. I'd assume this interviewer will be the same. I personally refuse all invitations where the person doesn't bother to change the default message. Even then I'll only accept if I really want that connection.
As a seasoned Sales Manager, with F500 experience, I would recommend that you review the profile of each person you will interview with, a day before your interview time, if poss. See if there are any mutual connections to pull from, and if so, reach out to them for a reference if appropriate.
At the very least, you are doing your due diligence to learn more about your prospect (the interviewer). IMO, interviewers should appreciate when they see that you looked them up on LI. Good luck!