First, you need to measure the space and take into account its length, width and depth. Next, start exploring the shops to see if you can find elements combine to meet your criteria. Make a plan with the various possible combinations.
You should preferably place the modules that will support the most weight, for example books, closer to the ground and the ones that will hold ornaments and lighter decorative objects to the top. Make sure the colors of your shelves matches the existing color palette of the room. Contrasts are a great idea, because the shelves will be more likely to attract attention.
When it comes to cabinets for your living room, the basic rule is to choose them in sizes that are proportional with your room, in order to avoid creating a cluttered look. On the other hand, cabinets that are too small compared to the room will give the impression they are lost in the décor, so should be avoided as well.