Once she studies your hair, its condition, its style, its cut, and your lifestyle (e. g., how much time you plan on spending on your hair each day), she will then make some recommendations for color and maybe even a more suitable style for you. Plan on being there for a few hours.
Almost as important as the color choice is deciding how you will get there. Is this dye job a DIY project or will you put your tresses in the experienced hands of your colorist at the salon? The price tag can be considerably different depending on which direction you go.