What is the best way to level up an Infernape FAST in pokemone diamond DS?

1. Use the Exp. Share. The Exp. Share is a held item that gives all Pokémon in your party experience points for battles, even if they don't participate. Give the Exp. Share to Infernape and let it gain experience while your other Pokémon do the battling

2. Battle wild Pokémon. Fighting wild Pokémon is a great way to gain experience, especially if you can find ones that are higher level than Infernape. You can also chain battles together to increase the amount of experience you gain.

3. Use Lucky Eggs. Lucky Eggs double the amount of experience points your Pokémon gain, making them very helpful for leveling up quickly. Try to use Lucky Eggs whenever you're grinding for experience.

4. Visit the Pokémon Day Care. The Pokémon Day Care is a place where you can leave your Pokémon to be trained. Your Pokémon will gain experience without you having to do anything, making it a great way to level up Infernape while you're doing other things.

5. Use Rare Candies. Rare Candies are consumable items that raise a Pokémon's level by one. They're rare and valuable, but they can be a great way to quickly level up Infernape if you have some to spare.