A Driver (or drivers) in NLP is a distinction of submodalities. When you have done the process of mapping across, you can then find out which are the critical submodalities that make a difference to your clients internal representation.
To find a driver or drivers you have to have access to your clients unconscious mind. I call that the “control panel”. Asking the questions, “how do you represent that?” when asking about a specific issue, “is a picture, sound, or feeling?” will gain access to their control panel and allow you to investigate the inner meaning which is held in images, audio and kinaesthetic properties.
A driver is the difference that makes the difference. To test drivers, when asking the question “how do you represent that?”, and your client comes up with an internal representation, you simply eliminate each sub-modality that does not make any difference to the inner ‘story’. If asking “is it black or white or colour?” and they say “colour” – then ask then to change the inner representation to black and white, to see what difference that makes.
If it makes no difference – visual/colour isn’t a driver. If it makes a big difference to the meaning of the issue, then yes colour is a driver, or one of the drivers! Replicate that process with all the submodalities, sounds, feelings and even the AD part (inner voice). You can sometimes get to submodalities and therefore drivers through the eye patterns.