In the United States, Flag Day is celebrated every 14th of June. It is not an official federal holiday, but some states consider this as a state holiday. Many would hold events and parades during the day or the whole week. Participating in such activities is mandatory, but as a free American citizen, you are expected to at least, raise the American flag on your home or put a small one on your office table.
This would show that you value the freedom the flag has given to you. It will also serve as a reminder that to be united with your fellow Americans just like the stars in the flag for the betterment of the country.