|All images in this post were found on Pinterest.|
Height matters: the height of your coffee table should be the height of your sofa cushions.
The size of your space will help narrow down materials and scale:
Big spaces = more dark/solid materials & larger pieces.
Small spaces = lighter/softer materials, smaller moveable pieces.
Upholstered pieces can be used in either small or large spaces, but you may choose a different material for each. You may also use one large ottoman for a large space; whereas in a small space you might use a long narrow piece that fits the length of your seating and offers a place to put your feet up without overpowering the room.
Glass tables are great for small spaces because they give the illusion of being very light and small. However, in combination with heavier metals, and in pairs, they are great for big spaces as well.
Your general style will dictate the rest. Whether you use natural elements of wood, a lacquered finish, or maybe even a marble top.
Whatever you choose, happy picking!