Get tails on coin:
Press Up just before the opponent's coin is displayed when battling an opponent. If done correctly, it will land on tails most of the time.

Free booster pack:
To get a free booster pack, go to your PC.

Unlimited energy cards:
In Dr. Masons Lab, both Sam and Aaron will give you a pack full of energy when you defeat them/ Sam only plays with two prizes, making him faster to defeat.

Charizard card:
Select the Charmander and Friends deck at the start of the game.

Booster packs:
Professor Mason will give you a booster pack after every email that he sends you.

Talk to the Club Leaders but do not duel them. Check your email and you will get a letter with a booster pack. This works with everyone except the Electric Club leader.

Get different cards from Professor Mason:
Save the game before reading the email from Professor Mason. Whenever you get a type of card you do not want, reload the game. The cards will be different when the game is resumed.

Energy booster pack:
After getting your own deck, go to Sam and offer to play a real duel. You will use the same practice deck and the flow of the game will be the same as during the tutorial. If you win, you will get booster pack full of energy.

Familiar face:
When you go to the Psychic Card Club there is a person in green. He is your character in the Red, Blue, and Yellow versions of Pokemon.

Walking faster:
Hold B while walking to move faster.

Faster card shuffling:
Press B if you do not want to wait for the cards to be done shuffling.

Imanuki card:
Go to each club lounge until you find Imakuni. Then battle him to get four booster packs for each victory. However, he may instead give you his Imakuni card. Repeat this until you have most of the cards needed to build a healthy deck.

Challenge prizes:
Go to the top center of the game map to find the Challenge Cup. You can compete in the Challenge Cup located in the Challenge Hall after you obtain your 3rd and 5th medal. If you battle there, you will get a rare card. It is hard to get in, because it is usually closed. Keep on visiting after every battle. If you enter you, will fight three trainers. The third one will be Ronald if you did not beat the game. After you beat the game, Ronald will not appear. These are the cards that you can get:

Mewtwo Lv. 60: The one that comes with the Pokemon VHS
Mewtwo Lv. 60: The one obtained if you went to the movies
Mew Lv. 8: Game Boy only
Surfing Pikachu Lv. 13: Game Boy only or Japanese card
Surfing Pikachu Lv. 13: Same as above, but a different number
Flying Pikachu Lv. 12: Game Boy only or Japanese card
Ivy Pikachu Lv. 16: Promo #1
Slowpoke Lv. 9: Game Boy only
Jigglypuff Lv.12: #2
Pikachu Lv. 16: You get it if you went to the movies
Electabuzz Lv. 20: You get it at the movies
Super Energy Retrieval: Game Boy only
Card Pop! Specials:
The following very rare cards are only obtainable in Card Pop!.

Lv.15 Mew HP 50
1. Mystery Attack (Does a random damage or may cause random effect)

Lv.64 Venusaur HP 100
1. Pokemon Power: Solar Power (Cures both Pokemon from an effect)
2. Mega Drain (Does 40 damage, removes damage equal to half of damage of the defending Pokemon)

Grand Masters victory:
When you defeat the Grand Masters, go to the deck machine on the top of the screen before you get the cards to build a strong deck. If you do not do this, the game will proceed to the credits and you will have to battle again,

Fire Club trade:
To get the Lv.9 promo Slowpoke easier, put all of your energies except one in temporary decks. Then, talk to the boy. He will reveal the location for only 1 energy.

Defeating the 8 Club Masters:
Gene of the Rock Club: use a grass and water deck
Amy of the Water Club: use a lightning and fighting deck
Isaac of the Lightning Club: use a fighting and colorless deck
Nikki of the Grass Club: use an all fire deck
Rick of the Science Club: use psychic and lightning deck
Murray of the Psychic Club: use a psychic and colorless deck
Ken of the Fire Club: use a water and fighting deck
Mitch of the Fighting Club: use a psychic and colorless deck

Defeating Ronald:
After you defeat the four Grand Masters, you will battle Ronald. He got to the cards one step ahead of you. Ronald's deck already has the four legendary cards, and thus is difficult to beat. Use Hitmonlee's (Lv. 30) Stretch Kick and knock out Ronald's benched Pokemons one by one. This is best done when he has his Kangaskhan on the arena, because he will need four energy cards to retreat. Since this kick does not apply resistance on the benched Pokemons, they can still be hurt even if they have resistance to Hitmonl(Fighting).

More cards from the Grand Masters:
After defeating the four Grand Masters, go back and fight them again to win more cards.