Assemble your tools. Purchase a laser level. It saves time and aggravation when hanging the art. This won't cut out all of the math and pre-planning, but it makes the job much easier.
Decide how high you want to hang the paintings. If your walls are a fairly standard height, the generally accepted distance to hang art is 66 inches from the floor.
Measure your selected height. Start from the floor and measure up the wall. Mark the height on the wall every few inches. If using a laser level, set the level at your selected height.
Determine the placement of each piece to be hung. If all the paintings are the same shape and size, determine the order you want them along the wall. If the pieces are different sizes, make templates of the artwork by tracing the outer edges of the canvases or frames on butcher paper. Use a gum fixative to hang the shapes on the wall. This gives you an idea of what the art will look like on the wall. Work with the order until your arrangement of shapes and sizes appeals to you.
Start with the piece to be hung in the center of the line. Look at the back of the frame. Measure the distance from the hanger or wire to the top edge of the canvas or frame.
Measure this same distance down from the laser line or line mark on the wall. Use a pencil to mark the spot.
Set the picture hook into the wall. The bottom of the hook's cradle needs to be positioned over the pencil mark in order for the top of the frame or canvas to be level with the marked line on the wall.
Repeat Steps 4 through 6 to hang the rest of the paintings.