A baseball player will notice you once you enter Route 9. He will throw TM 59 Fling at you. Fling does damage according to the item the Pokemon holds. The held item is thrown at the opposing Pokemon, so it is discarded after the move hits. There is a Biker riding around on the main road to the east.
Northeast of the team is Shopping Mall Nine. It's a big department store that sells medicines on the first floor, TMs and mail on the second floor, and battle items and stat-raising items on the third floor. There are also trainers to battle.
The Worker on the third floor will give you a Thunderstone. The basement, accessed by the eastern doorway on the first floor, is where you can change Rotom's form. There is also a PP Up east of the Janitor.
Back outside on Route 9, A biker is riding on the main path southeast of the mall entrance.
Go to the south side of the white fence. If you follow the fence west you will eventually find an HP Up. Southeast of the HP Up is a Full Restore. There is a cave to the west that can't be entered until you defeat the Elite Four. Head back to the main road and walk through the eastern passageway to Opelucid City.