You are unlikely to fight a Shadow Dragon in favorable conditions, being sunlight. Unless you are the rare exception of a champion actively wielding force, radiant, or psionic damage, then you will desperately need to raise the light level. The shadow Dragon will also actively flee the light spell's radius, as a Shadow Dragon constantly moves through the shadows.  Focus on clearing any Undead Shadows as these creatures are not terribly strong but can cause a nightmarish problem as they can sap players of their strength. Next, protect your Spellcasters, as that will be the dragon's first focus.  Cut off the Shadow Dragon as best as the party is capable of preventing him from fleeing or setting up choke points using multiple light-casting spells.