Interior Design in general is one of a few professions that has both aesthetic and philosophical disciplines. For that as an interior you have to create a well-crafted design that enhance the function and quality of the interior spaces, which could make the space easier to understand, therefore, the experience of such a space could lift up the spirits.
When you have someone's home to design, you have some points to consider very well:
1- Mentally and Emotionally: you now have intimate access to his/ her home and way of life, this trust is a Privilege, also a huge Responsibility.
2- Physically and Practically: you have to decide your decorating style, accordingly do your space planning, and determine your best layout, then choose the color scheme, determine flooring requirements, then select your wall treatments, determine light requirements, complete any repairs or renovations, and choose the window coverings, arrange the furniture, then accessorize, and finally evaluate the decorating.
It was a long answer to your question, i know, but i read some articles and books that helped me to find some good phrases. I suggest you read " Fab Job Guide to become a decorator", really good one to read.
the most important thing is that you know your client perfectly so you can reflect there personality and wishes in the design because home is where they should feel belonging and comfort, and that is very challenging to do.
As Home is considered the main space in Human life ,, so Home Designs can Be summarized in two words :
1 - Elements of Comfort :
Home designer must get sure to use comfortable Elements such as : Furniture , Wall Colors , Flooring Tiles , etc... ,,, All these Elements should be Harmonious together in shape , Distribution and colors to give The space user the most comfortable sense
2 - Space saving
In the last few years Living spaces have been getting much more narrow and less in space area . So Home Designer should be more creative to use Smarter Furniture that saves area and be most useful in space ,, also light wall colors and floor tiles should be used to give the sense of a wider space area
Finally Wall colors and decoration types should vary due to space usage , for example designer shouldn't use Fire colors like red or orange in sleeping or rest rooms but calm colors like light green and light yellow so the user gets Psychologically comforted
The most important is to keep in mind the combination between beauty, form and function like if you are about to design dinning room function must be the guide to design the suspended ceiling, lighting distribution and flooring tiling.
The most important thing you should put in mind when you come to Home Designing is that "it's not your home" ...Positively of course :)
In other words " you are designing for the comfort & liking of your client not your own"
While something/ some design aspect would be amazing to you, it might not appeal to your client taste or even comfort, and they might even tend to choose something that is totaly incoherent (aesthetic wise not production wise)....
so beside the other important design factors and points to consider from comfort functionality ...etc.
accepting this fact, will make the process alot smoother & more productive :)