Pokémon Diamond and Pearl/Route 204 & Ravaged Path

Route 204
After returning to Jubilife after getting your first Gym Badge, head north to Route 204. This route contains many items and wild Pokémon. Route 204 is divided into two parts: one below the Ravaged Path and one above.

Items

 * Sea Incense: To get the Sea Incense, you need Surf. Surf on the pond in the bottom-left corner of the route. The Sea Incense is on a ledge at the bottom.
 * Paralyze Heal: When entering the route from Jubilife City, walk on the right side of the fence. Go through the grass on the right edge of the pond to reach the Paralyze Heal.
 * HP Up: To get this item, you need Surf. Surf on the top pond in the lower half of Route 204. On the right side of the pond there is a small ledge holding the HP Up.
 * Awakening: After exiting the Ravaged Path, you will come across an Awakening lying directly in your path.
 * TM09 (Bullet Seed): To reach TM09, go to the very top of Route 204, before you reach Floaroma Town. There will be a fence to your left with a small gap in it. Walk through the gap to find the TM in a small alcove.
 * TM78 (Captivate): To get TM78, you need cut. From Floaroma Town, go down into Route 204 and cut the small tree just below and to your right. The lady behind the tree will give you a lesson on Pokémon genders and TM78, a move that works only on Pokémon of the opposite gender.

Ravaged Path
From here, all you need to do is go to the right and use Rock Smash on one of the rocks. Exit through the newly accessible doorway. You may also go to the left to pick up some valuable items, although most cannot be reached until you can use Surf outside of battle.

Items

 * Antidote: The antidote is directly in your path when you try to exit. In Platinum version, you pick up a Potion.
 * TM39 (Rock Tomb): This TM is accessible after you have Rock Smash. Go to the left after entering the cave. Rock Smash past a few rocks, and the TM will be just to your left.
 * Luck Incense: This item requires both Surf and Rock Smash to obtain. From the entrance, go left until you reach the lake. Surf north until you reach a piece of land. Go left, up, and right, Rock Smashing as you go. The Luck Incense will be in a small alcove to the right. Hop down the ledges to get back to the lake.
 * TM03 (Water Pulse): Start at the ledge where you get the Luck Incense. This time, Surf to the right, then go up to find a small ledge holding the TM.