"He who loves purity of heart, and whose speech is gracious, will have the king as his friend." Proverbs 22.11
I have read and practiced this verse for years. It seems to be the biblical version of "how to win friends and influence people." Two things are listed--purity of heart, graciousness of speech.
Purity of heart is about focus, about the "one thing." Remember in "City Slickers" when Billy Crystal asks Jack Palance what the secret of life was, the crusty cowboy called "Curly" holds up his finger. "Your finger?" asks Crystal? "No, find one thing, and do it well."
When our heart if focused on the "one thing" of the kingdom of heaven, it stands out. People take note.
Graciousness of speech is about valuing the people you talk to, and treating them as more important than yourself. It is about eye contact, listening, and genuine concern. It is never about shouting from a distance, the characteristic of all too much of today's Christian leadership in the US.
In short, being the friend of kings is about relationship. Being the kind of person, day in and out, whose heart is focused on the kingdom and who speech reflects concern for the other person.