1. Pokemon Centers: These are locations found throughout the game where you can rest your team and fully restore their HP and PP (Power Points). You can also deposit and withdraw Pokemon from your PC Box at Pokemon Centers.
2. Rest: Certain Pokemon moves, such as "Rest," allow a Pokemon to fall asleep and wake up after two turns, fully restoring its HP. However, the Pokemon will be asleep during those two turns and vulnerable to attacks.
3. Restoring Items: There are several items in Pokemon Diamond that can be used to restore HP, including potions, super potions, hyper potions, and max potions. These items can be purchased at Pokemon Centers or found as loot from defeated trainers, wild Pokemon, or within the game world.
4. Healing Moves: Some Pokemon learn moves that can heal themselves or their allies, such as "Recover," "Heal Pulse," and "Synthesis." These moves can be used in battle to restore HP.
5. Status Effects: Certain status effects, such as poison or burn, can gradually reduce a Pokemon's HP. Curing these status effects can prevent further HP loss. Antidotes and Burn Heals can be used to remove these status conditions.