As I've grown older and more experienced, the greatest of all lessons learned is how simple most things in life really are; and yet, how we try our darndest to complicate them. In part, I'm sure that's because we feel complicating anything makes us more valuable. 
Which is why coming across a recent Harvard study, described in an HBR article, impressed me. The research looked at the role of asking questions in interpersonal relationships. It found the simple act of asking questions is one of the most important aspects of trusted and open relationships, higher emotional intelligence, and learning. 
Before I dive into these findings, I'd like you to stop for a minute and think about the people with whom you have the closest relationships. These are not just the longest-standing relationships or those people you happen to be with most frequently out of necessity, but the people you genuinely look forward to getting together with--the ones who stimulate your mind and create a feeling of connection and emotional bonding. 
I'll bet that if you think about the sorts of conversations you have with people who fall into this inner circle of advisers, confidants, and perhaps even soulmates, you'll discover one thing stands out in how you communicate: the role of questions. You're more likely to ask questions without reservation of them, and you're more likely to enjoy having them ask questions of you. There is a mutual exposing that happens when you do this, and it uncovers not only a level of authenticity in how you reveal yourselves to each other, but also in how you arrive at ideas, answers, and insights you would not have likely arrived at on your own.
That essential chemistry is at the heart of what Harvard researchers Alison Wood Brooks and Leslie K. John uncovered. 

So, where'd you learn to question? 

Learning how to ask questions is not something that most people are taught, not unless you're a lawyer, in law enforcement, a doctor, or a journalist. That's not to say any of those professions has a universally applicable formula for how to best ask questions, only that in each case it's critical to shift the focus of the conversation onto the other person in order to build the rapport and transparency needed to make the relationship an effective one. 
The bigger and more important question -- the puns are just unavoidable, right? -- is how to use questions in cases where a longer-term relationship is the objective. 
What Brooks and John discovered was not remarkable in and of itself. We all understand that empathy and interest in another human being shows we want to better understand them. Yet how we best ask questions that illustrate that empathy sincerely is not something we necessarily practice, and if we do, we may still be going about it in the wrong way. 
To help, Brooks and John present these guidelines, from their research, for how to best ask questions that form a solid foundation of bonding, trust, empathy, transparency, and emotionally intelligent intimacy.

Favor follow-up questions.

According to Brooks and John, there are "four types of questions: introductory questions ("How are you?"), mirror questions ("I'm fine. How are you?"), full-switch questions (ones that change the topic entirely), and follow-up questions (ones that solicit more information)." 
All of these are fair game and have their place, but follow-up questions are especially important because they signal an interest in the person you are talking to. The opposite is also true. If you ignore follow-up questions and simply stick to an agenda of pre-scripted questions, the conversation turns into an inquisition at worst and a disinterested, awkward exchange at best. Also, keep in mind that when someone answers a question they are often opening the door a little wider in the hopes of revealing information that they want to share more of.

Know when to keep questions open-ended.

We've all heard that open-ended questions are better than simple yes/no or multiple choice questions, since they result in richer and more revealing answers. That's true, however, what we often ignore is the risk of closed-ended questions that introduce bias and a sense of manipulation.
We've all been on the giving or receiving end of questions that are subtly trying to drive to an already anticipated conclusion with the use of closed-ended questions. I have one good friend who's notorious for both asking and answering closed-ended questions in a way that almost makes it appear as though my being there is optional! When you ask a question stop, wait, and allow the person to digest and respond. Don't try to just fill the silence or move away from what appears to be a dead end. For example, one of the best ways to do this is by following-up a closed-ended answer, such as yes or no, with the question, " Can you tell me why you answered yes (or no)?" 

Get the sequence right.

One of the most interesting findings of the research was that the order of questions has a significant effect on how people respond. For example, if gaining insight and just getting information--regardless of the longer-term relationship--is the objective, then starting with the toughest or most invasive question first is the preferred method. This is because if you start with a really tough question the rest will seem less invasive. 
However, in relationship building the opposite is true. We need to build up to intimacy,  trust, and transparency. The researchers use the example of the work behind a viral Ted talk about the 36 questions that would make two people fall in love. The 36 questions were based on work they describe it in their HBR article, 
"Arthur Aron recruited strangers to come to the lab, paired them up, and gave them a list of questions. They were told to work their way through the list, starting with relatively shallow inquiries and progressing to more self-revelatory ones, such as "What is your biggest regret?" Pairs in the control group were asked simply to interact with each other. The pairs who followed the prescribed structure liked each other more than the control pairs. This effect is so strong that it has been formalized in a task called "the relationship closeness induction," a tool used by researchers to build a sense of connection among experiment participants."

Use the right tone.

Of all the things we do to help open up or shut down a conversation, tone has to be among the most critical. The findings here is exactly what you'd expect, "People are more forthcoming when you ask questions in a casual way, rather than in a buttoned-up, official tone." 
But what's especially interesting is that this applies across the board to all sorts of communication, even online questions and surveys. The researchers talk about an online survey in which some study participants used a very conservative and official-looking survey page while other participants used a fun and playful page. According to the research "Participants were about twice as likely to reveal sensitive information on the casual-looking site than on the others."
Of course, as with any strategy to open people up, this too cuts both ways. In fact, the sorts of apps used to gather personal data via social media, leading to the Cambridge Analytica fiasco, came from exactly these sorts of playful interactions with seemingly trivial game apps.

Pay attention to group dynamics.

It's not always the case that you're asking questions one-on-one. When a group is involved, the responses will necessarily be influenced by that group. What's interesting is that it usually takes only a few people to be either especially closed or open, in how they answer questions, to influence the entire group. The other thing researchers found was that third-party observers to a conversation tend to like the person answering the questions more than the person predominantly asking them. The reason here is that the questioner isn't giving up much and may come across as arrogant or aloof. 
The research also delves into what makes answers to questions meaningful and productive in furthering a sense of equity, bonding, and sharing. The bottom line seems to be that you need to strive for balanced transparency and sharing. An imbalance, one way or the other, can tilt the conversation and create discomfort or skepticism as to the motives of the questioner. 
All in all, this isn't complicated stuff. Yet I'd suspect that if you made an effort to keep track of what you're asking, how you're asking it, and the degree to which you're actually following these guidelines, you might be amazed at how often you stray from them. 
We all want to feel someone is interested in us. We all want to share that which we feel is uniquely us--the things that makes us valuable people. We all want to connect with people who are trustworthy, and we want others to see us as trustworthy.  
In a word, ask the right question. It really is that simple; don't complicate it.