A helpful guide from National Geographic Magazine on the proper display and care of the colors, published in 1917:

While there is no federal law in force pertaining to the manner of displaying, hanging, or saluting the United States flag, or prescribing any ceremonies that should be observed, there are many regulations and usages of national force bearing on the subject.

In raising the flag it should never be rolled up and hoisted to the top of the staff before unfurling. Instead, the fly should be free during the act of hoisting, which should be done quickly. It should be taken in slowly and with dignity. It should not be allowed to touch the ground on shore, or the deck of a ship, nor should it be permitted to trail in the water or in the dust. It should not be hung where it can be contaminated or soiled easily, or draped over chairs or benches for seating purposes, and no object or emblem of any kind should be placed upon it or above it. Read more