Press L1, R1, L1, Circle, R1, Triangle, L1, Select at the bridge screen.
All Ships
Press L1, Square, L1, Square, R1(2), Circle, Select at the bridge screen.
Attack Star Ships Without Them Returning Fire
Once you knock the shields down on the Enterprise or any ship that resembles the Enterprise (the constitution class ships), that you can position your fighter right behind the ships "saucer section" and fire at the impulse engines. Nine times out of ten, the ship you are attacking cannot return fire because you are positioned away from their phasers. An addition perk to this is that other enemy ships cannot fire at you because if they do they risk hitting their own allies.
Cheat Mode
You must be on the menu screen that looks like you are on the bridge of the Excelsior to enter the following codes. When you do, a text response will appear in the top right corner of the menu to confirm correct code entry.
Defeating Romulan Starships
When encountering a Romulan or Klingon Warship, disable their sheilds, then fly just beyond the neck, to the main part of the hull. If you keep your ship moving back and forth while firing, the ship will either be destroyed or cause them to flee.
Destroying Starships
When you intercept a starship and are having trouble destroying it, fly up behind it. They all have phasers on the back, so pull up beside an engine. Concentrate your fire on that engine. If done correctly, you will not get hit while destroying the starship.
Invincibility
Press L1, Circle, L1, R1, Triangle(2), Circle, Select at the bridge screen.
Kobayashi Maru Difficulty Setting
Press L1, Triangle, L1(2), Square, Triangle, R1, Select at the bridge screen.
Level Select
Press R1, L1, Circle, Square, L1, R1, Triangle, Select at the bridge screen.