Look for the most updated lists of easter eggs (lines of digital code), unlockables and glitches on gaming sites like IGN and Gameplanet. These gaming websites not only publish interviews, videos and reviews, but also comprehensive lists of special game features and how to get those games.
Use easter egg cheats by pressing a very exact sequence of buttons as the game loads. Common easter eggs might be anything from special guitars (like the game controller or an air guitar) to different crowd special effects. They can be helpful in beating songs or just fun diversions to mess around with in your spare time.
Find out the requirements for unlockable cheat codes and items. Unlockable items are the largest category of special game features like crowed effects and include guitars, special characters and even a song or two. The requirements differ for unlocking each and every item. You might need to complete the game in medium difficulty, or get 5 stars on a certain number of songs to be able to get the unlockable item.
Use practice mode to improve your skills on songs that you need to pass or get 5 stars for certain unlockable features and items. You can also search online for tabs or maps and sequences of the notes in a song to practice the button sequence slower and at your own pace.
Visit gaming sites frequently for updates, because more cheats and glitches are discovered as more people play the game and as time goes on more are unleashed from the creators of the game.