Erasing old sun damage is a pretty common request in my Florida practice, and the answer really depends on how much skin damage you have as well as your skin tone. Everyone should start with SPF since preventing future spots is important, and this can make any lightening treatment more effective.
Lightening creams like Retin-A, hydroquinone, and non-prescription lighteners can work, but these are best used under the direction of a physician, and everyone tolerates them differently. They can be very effective as a stand alone treatment for some. However, depending on skin tone and severity of pigment, for others they are better used as preparation or follow up for a more intense treatment like a peel or laser.
The lighter your skin, the less risky it is to use peels, IPL (intense pulsed light) or laser to lighten the pigment. Patients with light skin and dark spots respond best to these treatments. Patients with darker skin tones may find that these treatments can remove more pigment than desired and may be better off sticking with the topical creams instead.