There used to be a trend of people attending assertiveness training. Most often these were people who were shy, timid, and unsure of themselves. They would learn a variety of skills to use, go back into their lives and continue to be shy, timid, and unsure of themselves.  

NLP doesn’t teach tricks or tools to use at the moment, what you will gain from NLP is not just a conscious ability to do something different, but more importantly, a neurological mindset that is wired to new behaviors in different situations.  

The main reason a person would need to increase their assertiveness skills is if they have a set of beliefs that do not allow for assertiveness as a reactionary trait. These beliefs lead to various behaviors, habits, emotions, and skills which ultimately can be changed at the unconscious level.  

By understanding the unconscious beliefs and programs of a person, you will be able to identify what type of communication is best for delivery as well as a variety of NLP exercises that will clear or resolve any interference to being assertive in the first place.