Choosing your Starter
At the beginning of the game, you are in your house with your male rival, Cheren. You are waiting for your female rival, Belle to show up. When she does, both of your rivals urge you to open your birthday present from Professor Juniper[. In the box, you will find three Poké Balls (Containing Tepig (Fire Type), Oshawott (Water Type), and Snivy (Grass Type). This is where you choose your starter Pokemon. Choose whichever you like the most, since--for the first time in a Pokemon game--none of the three will give you a distinct advantage in the first two gyms. Once you choose, your rivals will take the other Pokemon. The male rival will receive the Pokemon with the type advantage to yours, while the female rival will receive the Pokemon with the type disadvantage to yours. After you select your Pokemon, a battle will ensue with your female rival.
~Belle~
If you picked Snivy;
Oshawott Lv. 5
If you picked Tepig:
Snivy Lv. 5
If you picked Oshawott:
Tepig Lv. 5
Beat her, and collect P500. After the battle, your room will be a mess. Nonetheless, your male rival will heal your Pokemon, and then challenge you to a battle.
~Cheren~
If you picked Snivy:
Tepig Lv. 5
If you picked Tepig:
Oshawott Lv. 5
If you picked Oshawott:
Snivy Lv. 5
These first two battles aren't much, considering the only attacks the Pokemon know are Tackle and either Leer or Tail Whip. After your second battle, your male rival will storm out of your room, upset that he lost. Follow him outside.
He will be downstairs with Belle and say some stuff before leaving. In your home town you have to go to Belle's house and her father will be yelling at her like an idiot before she goes off to Prof. Juniper's lab. Now you need to go to the lab as well and get the Pokédex. As you leave the lab, your mom will show up and gush about how proud she is of you before giving all three of you a Town Map, which lets you take a look at the Unova region in depth. Go ahead and open it (it's in your Key Items pocket) if you'd like.