The best way that I've found to get into that state of mind is simply to practice. Don't get stressed out if it doesn't work, or if you forget, since you're only practicing at it... but practice makes habit, and if you refine the methods that you use to practice, you'll have a pretty good habit out of it when you're done.
NLP, etc., are all very good 'generic' methods to practice finding the 'gap,' but really, nothing beats finding your own method. You can start with the generic methods, but refine them and actually study what parts really work for you and don't be afraid to discard the parts that don't work.