Scale and proportion can be tricky. Most things we use everyday are scaled to work with the proportions of the human body, such as door knobs and light switches. Furniture and lighting on the other hand can be a challenge.
It is always a good idea to have different scaled seating available for your different sized guests. However, it is essential the seating height be similar around the room. If your seating heights are more than 3 inches different, your guest will feel uncomfortable. One person will be higher and looking down. This is a popular ploy for people who want to intimidate others, but hopefully, not in your living room! Also the level of occasional tables should be similar to the arm height of chairs and sofas. This makes it comfortable for placing a cup, glass, etc. If tables are too high or low, spills will be frequent.
Overhead lighting should not be the only light source in your room. Even in the smallest of spaces, a table lamp is a welcome addition. You want to think of the idea of layering when it comes to lighting. Overhead lighting fixtures or chandeliers are the beginning of the layers. If you are able to put lighting on a dimmer switch, all the better. Next, you need to have task lighting, usually for reading or highlighting different areas in the space. Generally the bottom of the lampshade should be about level with the eyes when seated. Also, it is important the tops of lamps are at similar heights. Placing a couple of books under a lamp to make its height similar to other lamps, often adds balance to the lighting plan.
These are a few practical tips to help ensure good scale and proportion for your space.