Okay, this is my first walkthrough, so don't be surprised if it sucks.

Pokemon: Diamond and Pearl Walkthrough
1: Intro
2: Walkthrough
2.1: Start to 1st Leader
2.2: 1st to 2nd Leader
2.3: 2nd to 3rd Leader
2.4: 3rd to 4th Leader
2.5: 4th to 5th Leader
2.6: 5th to 6th Leader
2.7: 6th to Lakes and 7th Leader
2.8: Lakes and 7th Leader to Mt. Coronet
2.9: Mt. Coronet to 8th Leader
2.10: 8th Leader to Elite 4
2.11: Battle Park and Legendaries
3: 'Freebie' Pokemon
4: Evolutionary Families
5: FAQ

1-Intro
"Welcome to the world of Pokemon. Pokemon are creatures with amazing powers." You know the rest. So why do you even care about hearing it and buying the same game again and again? It's obvious. Video games are fun and addictive. Come on. You know you want help beating this game. It gives you a sense of accomplishment. That's why I'm here.

Let's begin with the basics. There are seventeen different types, and Pokemon sometimes have two types. If you need any help with the matchups, here's a chart.

X=2x Damage, or Super Effective.
V=1x Damage.
I=0.5x Damage, or Not Very Effective.
O=0x Damage, or Has No Effect.
Pokemon Type I Normal I Fire I Water I Grass I Electric I Rock I Ground I Ice I Dragon I Poison I Bug I Psychic I Fighting I Flying I Ghost I Dark I Steel
Attack Type______________________________________________________________________________________________________________
Normal________|__V__|__V__|__V__|___V__|___V____|__I___|___V__|_V_|___V___|___V___|_V_|____V____|___V___|__V__|__O__|__V__|___I__
Fire___________|__V__|__I__|___I__|___X__|___V____|__I___|___V__|_X_|____I___|___V___|_X_|____V____|___V___|__V__|__V__|__V__|___X__
Water
Grass
Electric
Rock
Ground
Ice
Dragon
Poison
Bug
Psychic
Fighting
Flying
Ghost
Dark
Steel

2-Walkthrough
The game begins with Prof. Rowan explaining Pokemon to you, then asking for your gender and you and your rivals' names. Pick them, and soon, you can begin the game.