If you happen to hire the professional interior designer, you may be free to do the home decor yourself. But, you need to specify to the interior designer what you really want to achieve in your design. Make it clear about your choices of colors, the air that you want to feel when you’re in the particular room, or the furniture that you want to put in there.
All of these information really useful for your interior designer because she could get your point of view first before she gets to work. This will allow you to save both of your time so she don’t have to undo what she already made before just because you don’t like the color, or because you don’t want particular furniture being placed in the corner.