Start with costuming that mimics that which was worn by those who lived and fought during the Revolutionary War. Add props to these costumes including tricorn hats, long hair wigs, and thin, round spectacles to indicate the 18th century time period.
Since the war was of the utmost significance during the time period, make sure the props indicate this factor. Search high and low for used or vintage wartime weapons including muskets and daggers, rather shiny black hand guns. A decorative sword can give precedence and rank to the actor portraying General George Washington. Consider using drums and fifes, a type of flute, as well to indicate a regiment of soldiers.
The American flag, which had 13 stars to represent the 13 original colonies, is an undying symbol of the war and can be used as a prop to emphasize the time and place. Along with this flag, use the British flag to represent the King's opposing forces.