From StrategyWiki, the free strategy guide and walkthrough wiki

• The main objective in Pokémon is to catch Pokémon, which are randomly found in tall grass.
• In order to catch Pokémon, you will need to use Pokéballs, there are many kinds of Pokéballs but the basics are Pokéball, Great Ball, and Ultra Ball.
• Wild Pokémon are weak at first but get progressively stronger as you move across the Hoen Map.
• Some Pokémon are able of 'evolving', once evolved they will have a new look, higher stats and new moves.
• You can not catch other trainer's Pokémon, only wild Pokémon.

[edit] Controls

[edit] Overworld Controls

• - move in the appropriate direction (no diagonals)
• / - help
• pick up items, talk to people, etc.
• - pull out the menu
• - use a "registered" item

[edit] Battle Controls

• - Move around the battle menu
• / - help
• - Select an option from the menu(Attack, use item, switch Pokémon, run)
• - Go back