First, of course, head to the Pokemon Center. Simply follow the path east, then south, then east once more and you'll find yourself in front of the Center. Head in and heal your Pokemon, as well as stock up on anything you might need to. Once you're done, head back out so we can get onto exploring!
Head west first, out onto the grassy area with the two benches. Check inside the bin south-west of the lower bench and you'll find a Max Repel . From there, head north up to the left of the two buildings there. Enter it and move up to the second floor.
Talk to the guy near the top of the stairs and he'll give you a Poke Ball . Now head over and talk to the woman behind the desk. She'll ask you two questions about your starter Pokemon. One's about whether it's a certain weight and the other is about whether it's a certain size.
If you answer both of these questions correctly, you'll be give a Gem that matches the type of your starter. That's all to do in this building, so exit. Enter the building to the right of this one. Head up to the second floor and talk to the man in the south-east corner of the room to receive a BalmMushroom .
Exit this building. If you move up the stairs to the right of this building and enter the building at the top, you can listen to two musicians practising. If you want to listen to a nice little track, feel free to head up. Once you're done, head south from the stairs until you reach a set of stairs leading down west.
Move down them, then head west and enter the building at the end. Inside is a girl on the first floor who will ask for an Excadrill and who will trade a Level 40 Ambipom in return. If you make the trade, you'll then be able to battle her afterwards, taking on the Excadrill that you just traded.
If you win, you'll then be able to trade a Hippowdon and receive an Alakazam in return. If you do this, you'll be in a second battle taking on the Hippowdon you traded, along with a Level 63 Stoutland and Sandslash. Once you've done all you want to here, head back to the Pokemon Center.
Heal your Pokemon then head south into Route 1 !