Whether you are beginning with a home full of possessions or one empty room, you need to look closely at both the permanent features and personal items that will remain in the space.
Forget about what is in the room now and imagine the feel and functionality you want for the room. If you have a clear vision as you think about each of the different elements you own you will be able to make decision about the items you already own. So decide if you want to keep it long-term, keep it for now or lose it. Once you know what you are working with you can work to incorporate them seamlessly into your overall color scheme.
I usually recommend narrowing down your options to a color family or two. By narrowing your focus you will be able to put your energy into finding just the perfect hue in that color family.
In order to decide you need to take into consideration the elements in the room that aren't going to change. For instance the color will need to work well with the color of the flooring or carpet. It will need to complement any furnishings that are in the room or that you plan to purchase. It will also need to harmonize with the colors in adjoining rooms.
While there are many things to consider the good news is that all of them can help you to hone in on the perfect color by quickly ruling out some color families that you know won't work.
Also keep in mind that the color you paint your wall is a backdrop for the room and does not need to match anything exactly so don't worry about finding the exact yellow of the little square in your upholstery fabric and in fact it is often more appealing if it doesn't match exactly but rather harmonizes with the elements in the room.