Guitar Hero 5

First off you can not attempt any challenges on the beginner difficulty. You can attempt them at easy, medium, hard, expert or expert +(drums only). Each song in the career has a challenge associated with the particular song. Some challenges are for guitar, some for bass, some for vocals, some for drums, and some for a band. Examples of challenges are hit x number of snares on drums (x could be 100 for gold, 150 for platinum, and 200 for diamond for example), upstrum x number of notes on bass, hit x number of chords on guitar, or keep up a 4x multiplier for x number of seconds on vocals.

The easiest way to do this is to play on a difficulty you are comfortable with and you believe will contain enough of the stipulation needed for the challenge. For example if you need to hit x number of chords on a song you may need to play medium as opposed to easy to have enough available chords to hit.

You should work on getting diamond on each song as these will stack with the gold and platinum challenges.