Pokémon Ruby and Sapphire/Route 102

On the Way to Petalburg City
This is the first route in the game where you will encounter trainer battles and berries. If you walk in front of a trainer, an exclamation mark will appear above his head and he will challenge you to a battle that you cannot refuse. The positive side of this is that you gain more experience by defeating trainers than random encounters and you are rewarded money. The downside is that, should you lose, you will be returned to the most recent Poké Center you were at and you will lose some money.

During your travels you may encounter oddly shaped trees that contain berries. There are many different types of berries in the game that do different things. For example, on Route 102 you will find Oran berries and Pecha berries. The Oran berry will heal a Pokémon 10 HP and the Pecha berry will cure poison. The best part is that if you allow your Pokémon to hold the berry, it will be used automatically and you won't waste a turn using an item of your own. Remember, once you pick the berries you will have to plant a berry to make it grown into another full tree to get more.

As you traverse Route 102, fighting trainers along the way to pick up some money and experience, keep an eye out for a potion in the grass.