When a lady eats a hamburger, she first considers its size. If it's quite small, as in the photo above, she eats it as is. If it is larger, however, she first cuts the hamburger into more manageable halves, and if it is very big or has condiments that are likely to get messy, into fourths. Then, picking up one piece, she takes a bite about the size of a quarter (twenty-five cent piece) which can be neatly and comfortably chewed with her mouth closed. If there are toppings that threaten to spill, a lady removes them with her fork to the side of her plate and then uses her fork and knife to eat them.
Although in very casual settings it is acceptable to put condiments directly onto a hamburger, in business or more formal surroundings, it is proper to first pour a small amount of the sauce on the edge of the plate and then spread it on the hamburger with a knife.