One of the great pieces of kit in the NLP tool bag is the meta model.
It's a series of questions that can be used to clarify the speaker's intent or meaning.
The questions can also help bring about change at quite a profound level as they open up the speaker's thinking and can help get them in touch with what they really think and feel about something.
They do this by getting beneath the 'surface structure' of the words we use and by clarifying the meaning.
When someone (let's call her Penny), for example, says 'My boss always makes me cross', we know that

• Penny has a boss
• Penny is cross

And that is all we know.
Before we can have a meaningful conversation with Penny about this, we need to know more.
The meta model provides a framework for doing this by recognising the language patterns we use to

• Distort -this is where the speaker, with no ill intent, but rather as a result of muddled thinking, represents things in a way which may sound sensible on the face of it but when you analyse the words they just don't stack up.
  In this case, Penny has told us that her boss 'makes' her cross.
  That's not possible.
  'Being cross' is a feeling - it comes from within.
  Penny's boss can no more make her cross than he or she can make her red and white blood cells do their jobs properly - they are internal processes.
  For sure, Penny's boss may do something that trips an internal switch in Penny's brain that results in crossness - but all that is doing is activating a learned response.
  A response that can be unlearned if Penny is made aware of it, through sensitive and appropriate questions, and if she chooses to switch the trigger off and react differently in future.
  
• Delete -i.
  e.
  missing out useful information as the speaker chooses what to focus on.
  In this case, for example we don't know which boss (if Penny has, as some of us do, more than one).
  Nor do we know what 'cross' means for Penny (i.
  e.
  'how' is she cross'?).
  Nor do we know what Penny is cross about.
  
• Generalise - i.
  e.
  where the speaker takes a particular experience and applies it to a multitude of other situations.
  In this example, by saying her boss 'always' makes her cross Penny is effectively saying that in every situation, at all times, even - for example - without opening his or her mouth - her boss makes her cross.
  This is unlikely.
  It is more likely that there are specific situations or aspects of her boss's behaviour that are the trigger for her cross response.
  

Each of these three broad categories (distortion, deletion and generalisation) has a number of sub categories or different ways in which speakers distort, generalise or delete.
And for each category and sub-category there are a number of questions that are designed to get behind the surface structure and uncover the true meaning or explore the thinking behind what is behind said.
(You can find a more detailed discussion and examples here.
So, for example, if we go back to our example, we might ask Penny

• What are you cross about
• How are you being cross
• What is it about your boss that causes you to choose to feel angry (you need to be in great rapport to ask this one!)
• Which boss are we talking about
• Is there (and/or 'has there ever been) a time when you haven't been cross with/about your boss

The usefulness of these types of questions was really brought home to me when listening to Susan Scott, author of Fierce Conversations who reminded me that worthwhile conversations

• Interrogate reality
• Provoke learning
• Tackle tough challenges, and
• Enrich relationships.
  

Even if you have no formal NLP training, knowing something about the meta model questions, how and when to use them can be a potent way of developing your communication skills.
There are a number of ways you might consider doing this, including: not only formal NLP training but also

• Reading widely on the subject
• Using some of the meta model flash cards, and similar products that are now available at relatively low cost
• Listening intently to radio or television programmes (documentaries are good for this particularly when you're starting out, but with practice, you could do this with any programme) to identify each of the patterns and then consider how you'd respond to it - what question would you use?
• Watching some of the videos on the subject available on YouTube and similar sites.
  Do make sure, though, that you check out the credentials of the presenter first! Like so much on the internet, there is some really high quality stuff out there.
  And some dross, too.
  

The key to using questions - whether meta model ones or others - to help develop a fruitful and meaningful conversation is to use them

• Sparingly-as a condiment, to bring out the flavour, rather than as the main course.
  The idea is to have a conversation that flows naturally - rather than for the person you're talking with to feel they are under interrogation
• While in rapport
• When appropriate,, with a 'softening phrase' ('I'm curious...
  ' or 'just now when you said...
  I found myself wondering'..
  ..
  )

Questions are rather like DIY or hardware tools.
To get the best results, you need to choose the right one for the job and use it with care, skill and attention for: You can tell whether a man is clever by his answers.
You can tell whether a man is wise by his questions ~Naguib Mahfouz, Egyptian writer and 1988 winner of the Nobel Prize for Literature