Konami Code
The Konami code (also known as the Contra code) may be the most famous video game cheat of all time, because it was available in multiple games. It started in a game called Gradius, in which entering Up-Up-Down-Down-Left-Right-Left-Right-B-A-Start after pausing the game granted the player full power-ups at the game's resumption. The exact code could also be implemented in the same manner, or at a game's title screen, for other NES games like Contra, Top Gun: The Second Mission and Teenage Mutant Ninja Turtles III. Oftentimes, the Konami code granted 30 extra lives. The code lived well beyond the NES days and is occasionally still used in Konami games today.
Passwords
Some NES games offered the ability to enter passwords. These were usually awarded to a player who advanced a level. At the end of a level, a completion page would be shown with a password made out of numbers and letters. If the game turned off without warning or a player wanted to start a game at a later level, going to the password screen and entering in a specific password would automatically take the player to his desired stage. Some games also used passwords to enter in cheats like extra lives or supplies, secret characters or levels, helpful codes and fun secrets.
Title Screen
Some games required cheats to be entered while the game was paused, and others were entered at the password screen, but most of the time, NES cheats were entered at the title screen. This is where the title of the video game is on the screen, where a player can select to start game, change game options or select to go to the password screen. Most of the time, a sound will alert the player that a cheat has been entered correctly (usually a ding or musical tone).