Practice Makes Perfect
Before checking a walkthrough, bear in mind that for games like Guitar Hero III, nothing can act as a substitute for your own skills. The best tip you can get is to abuse practice mode, perfecting your ability to play a song without being disqualified for missing too many notes. Practice Mode also allows you to slow the song down, which is critical for learning to play sections with lots of notes in rapid succession or tricky runs of hammer-ons and pull-offs. While practicing is not the most fun aspect of the game, it is extremely useful helping you beat a song that you're stuck on and advancing your Guitar Hero skills to the next level.