When I started out at design school I really didn’t understand the difference between interior decorating and interior design. Interior decorating is what one would call the soft furnishings and embellishments. This usually includes the non-permanent items such as window treatments, furniture, paint, art, etc. Interior design includes everything inside the home including walls, fixtures, appliances, windows, finishes, etc. including the decorative items. Anything structural is in the realm of architects.
So, in my opinion, good interior design starts with a good floor plan. This is the framework of how one room flows into the next and defines how we live. Next, you have to figure out what type of furniture you are planning to put in each space. For example, in the eat-in kitchen can you fit a table for the number of people in your family? Will the master bedroom fit a queen or king size bed plus two side tables? Do you have enough storage for your needs? As you can see, you must define what you own and how you want to live. Once all that is in place, you can begin to add your personal touch to the space.
If you work in a dark office all day, maybe you want to come home to somewhere cheerful and bright. On the other hand, if you are surrounded with much activity during the day you may prefer to come home to somewhere more serene. But, as long as the floor plan makes practical sense and flows, regardless of how you finish your space, it will be good design.