The Ramchal spoke about the enormous importance connected with the sanctification of Hashem’s name. This is known as Kiddush Hashem.
The Ramchal in Messilat Yesharim was focused on how we are to work at our individual spiritual growth. Therefore, he did not address the idea of Kiddush Hashem on a national level. This had to do with glorifying G-d, and making His Name great among the nations.
On a personal level, one must always be certain that he conducts himself in a way that would make Hashem proud. He should be well mannered and well groomed. He should certainly conduct his business matters with the highest level of integrity.
The Talmud in Masechet Yoma, gave examples of Kiddush Hashem from various great Amoraim. Paying on time for a purchase was one example of Kiddush Hashem. Rav Yochanan felt it was necessary to go with his Tefillin on, all day. There was a strong emphasis on consistency and not being hypocritical.
There was the story of Rav Safra who intended to sell his donkey to a Gentile. He was offered the price he asked for, but couldn’t answer momentarily, because he was reciting the Shema. The Gentile thought his offer wasn’t high enough, and offered more money. When Rav Safra finished his prayers, he told his buyer, that in his mind, he accepted the first offer. In good conscience, he could not accept the higher offer. This is Kiddush Hashem.
We must remember that as observant Jews, we carry a great responsibility. There are situations, when we might meet secular Jews, and their total impression of a religious Jew, may come from that one meeting with you.
We must remember to act like Rav Safra, and bring honor and pride to G-d, and the rest of the Jewish people.