This is for outside flags (attached to a halyard and flown from a pole), not indoor/outdoor flags (for color guard flagstaffs for carrying only).
The American Flag
The American flag must always be folded into a triangle (ref: Flag Code). If it is wet from rain or snow, it is taken down, folded, and brought inside where it is unfolded and laid out to air-dry. Once dry, it is refolded, taken outside to be unfolded and raised.
All other flags are twice folded in half length-wise and then folded in half width-wise three or four times depending on their length. You should end up with a rectangle.
Flags on the same Pole- same halyard or double halyard
Depending on the number of flags being taken down (no more than two: US and state or US and POW), all of the flags (same pole) are taken down and gathered into different individual’s arms and then folded at the same time- or at least the American flag is folded first if not enough personnel are available at the same time.
Special State Flag Folding Procedures
The triangle fold is reserved for the American flag. It is not appropriate to straight-fold any other flag into a triangle unless dictated by the state. (for special folds, ref: Secretary of State, State Attorney General’s Office, state legislature, etc.) If your state has not dictated a special fold, you should fold it into a rectangle.
Subd. 6. Folding of the state flag for presentation or display. The following procedures constitute the proper way to fold the Minnesota State Flag for presentation or display. Fold the flag four times lengthwise so that one section displays the three stars of the state crest and the text “L’Etoile du Nord.” Fold each side behind the displayed section at a 90-degree angle so that the display section forms a triangle. Take the section ending with the hoist and fold it at a 90-degree angle across the bottom of the display section and then fold the hoist back over so it is aligned with the middle of the display section. Fold the other protruding section directly upwards so that its edge is flush with the display section and then fold it upwards along a 45-degree angle so that a mirror of the display section triangle is formed. Fold the mirror section in half from the point upwards, then fold the remaining portion upwards, tucking it between the display section and the remainder of the flag.
Subd. 7. Folding of the state flag for storage. When folding the Minnesota State Flag for storage, the proper procedure is to fold and store the flag in the same manner as the national colors.
South Carolina has a special fold developed my an SCNG Soldier. Click here for the South Carolina state flag.
Ohio’s state flag, which is actually a burgee, is actually folded 17 times!
Texas. Fold horizontally so that the red stripe is up and the white stripe down. Repeat another horizontal fold. The red stripe will now be on the inside and the white stripe on the outside, the blue field on top and the star facing down. Fold from the end like the National. Keeping folding the flag as such until the entire triangle is blue with part of the star remaining.
Maryland’s technique is just like the National.
Foreign national flags may have vastly different techniques. Do your research if that applies.