Dressing tables first appeared in France in the 18th century, though at that time they were known as "toilettes" (toilet tables.) Women would enclose their cosmetics in a handkerchief and deposit it in the chest of the table. Nowadays dressing tables are still used for their drawers and storage, and keeping them well lit is of the utmost importance, as this is where a woman applies her make-up. When it comes to lighting you have a range of choices.
If possible, make sure that your dressing table is near a window that receives direct sunlight, as this is the best form of light for your dressing table during the day.
Consider placing a table lamp on either side of the surface of the dressing table. Make sure that they are near enough to the mirror that their light is reflected and thus doubled. Buffet lamps are perfect for this as they are skinny and don't take up much space, yet have a powerful soft glow.
Consider installing a lamp in the wall on either side of your dressing table. Make sure that it is possible for the lamps to overhang the mirror so that it can reflect their light. The best way to do this is by purchasing "swing arm" wall lamps: with these you can adjust the angle of the lamps as you please.
Consider installing a light bar containing three or four light bulbs on either side of the mirror. This will give you plenty of illumination during the night, and give your dressing table a style reminiscent of Hollywood.