Learning about someone takes time.
You need to be able to have enough encounters with a person to observe what they say and what they do. If you only pay attention to one or the other, you will not have a balanced perspective of the person. By giving time and enough incidents, you will be given a chance to learn about someone and let them share with you from their mouth what their heart is and from their actions what their purpose is. You will be given the chance to see how their talk and their walk align.
If there is all talk and no walk, then I would begin to question whether you are falling for the words or the man.
Stay true to what they show you. Out of the mouth the heart speaks. Out of the actions the true motive is expressed.
What ways have you found to observe someones talk and walk?