To begin with the choice of colors would top the list. So what family of colors is on your mane wish list? Are you looking to alter the color or color the gray?
When you use the services of a real professional, go to the appointment with an open mind. You may have your heart set of pale blond, but if the colorist can prove to you that a deep strawberry is really your best shade, listen to her. She is trained to match color with skin tone. She knows what will work, and what won't.