Minecraft wiki entry for Superflat_survival, associated text: Rotten Flesh - Emergency Food Source.
Iron Ingot - Use to make Iron tools and Iron Armor
Carrots and Potatos - Don't eat them, farm them later for food and animal breeding.
Iron Sword - Good weapon. Only kill hostile mobs with it unless enchanted with fire aspect. If it has fire aspect, kill animals for cooked meat.
Iron Shovel - Don't dig dirt with it, use as melee weapon as it deals more damage than bare fists.