Namco Museum 64

99 continues:
Before playing one of the games, repeatedly press C-Right. You can get up to 99 continues.
Information in this section was contributed by JSwan6103.

Double fighter (Galaga):
Shoot one of the green ships on the top row to turn it blue. When one of them dives alone, avoid its shots. Intentionally allow your fighter to be captured by its tractor beam. With your next ship, wait until the joined ships to dive. Shoot the alien while carefully avoiding your captured fighter. You will have a double fighter with twice the firepower.
Information in this section was contributed by Rocket2u2.

Keep Galaxians unarmed (Galaga):
In level 1, allow all the enemies to get into formation and note the bottom left bee. Kill all of the other enemies except for that bee. When just that bee remains, place your ship in the lower right corner. Allow him to fly around and attempt to attack your ship. After one pass with him not firing, allow him to pass again. If he is still not firing, shoot him during this second pass. This will take approximately 15 minutes. Doing this will disarm the enemies for the remainder of the game.
Information in this section was contributed by The Big Moovoski.

Super shot (Galaga):
When the enemies fly onto the screen at the start of a level, press A wait very briefly, then press R. If done correctly, you will fire two shots with the single fighter. This can also be done with the double fighter. Do this while moving to spread out your shots.

Quick start (Pole Position):
Shift to low until you reach about 160 kmh, then press R to shift to high. This results in a nice speed boost and if you have pole position, an instant lead.
Information in this section was contributed by The Big Moovoski.