Pokémon Diamond and Pearl/Canalave City

Beware! As soon as you cross the bridge your rival will fight you. Heal at a Pokémon Center and save before the battle.

In the very first house you see when entering from the east, a girl will give you TM48 (Skill Swap). Above this house is the Pokémart, where there are new items being sold: Repeat Ball, Ultra Ball, Hyper Potion, and Max. In the house above the Pokémart the Move Deleter lives. Only he can delete HM moves.

Rival Battle
From the concrete, step onto the wooden bridge before your rival blocks you for a challenge. He starts off with his level 31 Staraviaand then his level 35 evolved starter (or fully evolved if you chose Prinplup as your starter). Afterwards he will send in a level 30 (Bug-Fighting Type), and then a level 32. Lastly you will fight his level 32 Roselia. This is quite an easy battle

Gym Battle
In this Gym, Steel Pokémon are used, so get used to using your Fighting, Ground, and Fire-Types. Poison-Type moves don't affect Steel Pokémon at tall.