Go to Kumkapi. It's a lively pedestrian area full of fish restaurants and gypsy music. Our favorite is Olympiat II. Go with a group so you can share. Take it slowly. Start with cold appetizers (selected from a tray), then a couple of hot appetizers (calamari for example), select your fish based on how you'd like it prepared... grilled, fried, stewed, salt-baked. Raki or beer to accompany. Be sure to mix your raki 1/3 raki 2/3 water with room for 2 ice cubes.