Finding the Legendaries
One of the hardest parts of "Pokemon Emerald" is finding all of the legendary Pokemon you need to move on with the story line. Groudon and Kyogre, captured by Team Aqua and Magma, need to be released in order for you to find Rayquaza. Defeat the Elite Four, and you will find Groudon in the Land Lair and Kyogre in the Sea Lair. Once you set them free and defeat Aqua and Magma, make your way to the Sky Pillar to find Rayquaza. In battle, you will have the opportunity to capture Rayquaza, so come prepared with plenty of Poke Balls.
Berry Master's Wife
One of the most valuable assets you can find in the game is berries. Different berries have different healing properties, and it's important to try to stock up with as many as you can to avoid having to constantly stop at the Poke Mart. East of Mauville City, visit the Berry Master's Wife once a day for a different berry to help you on your quest. Tell her "SUPER HUSTLE" for a Belue berry, "COOL LATIOS" for a Durin berry, "CHALLENGE CONTEST" for a Pamtre berry, "GREAT BATTLE" for a Spelon berry and "OVERWHELMING LATIAS" for a Watmel berry.
Catching Strategies
Catching Pokemon is the overall mission of each generation of the game. There are certain hints you can use to help you along in your efforts to catch all of them. First, if the Pokemon you are using in battle is a lower level than the Pokemon you are attempting catch, you are going to be at a disadvantage. To increase your chances of successfully catching it with the first or second Poke Ball you throw, wait until the opposing Pokemon's HP is in the red zone. Send out a Pokemon from your lineup with a move that can create a status problem, such as sleep or paralysis, to further increase your chances. Use Great Balls or Ultra Balls to have more success catching higher-level Pokemon later in the game. With these tips, you'll be able to complete your Poke Dex in no time.